BRS Gross Anatomy [9 ed.] 2018040144, 9781496385277

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I 11

Gross Anatomy

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Gross Anatomy

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NINTH EDITION

Nancy L. Halliday, PhD David Ross Boyd Professor Co-Director, Medical Human Structure Department of Cell Biology, College of Medicine

University ofOklahoma Health Sciences Center Oklahoma City, Oklahoma

Harold M. Chung, MD Asso date Professor of Medicine

VCU Health-VCU Medical Center Vlrginia Commonwealth University DMsion of Hematology and Oncology Cellular lmmunotherapeudcs and Transplantation Program Richmond, Vlrglnia

•Wolters Kluwer Philadelphia • Baltimore • New York • London Buenos Aires • Hong Kong• Sydney• Tokyo

I

Acquisitions Editor: Crystal Taylor Product Development Editor: Andrea Vosburgh Editorial Coordinator: Kerry McShane Marketing Manager: Phyllis Hitner Senior Production Project Manager: Alicia Jackson Senior Designer: Joan Wendt Rlustration Coordinator: Jennifer Clements Manufacturing Coordinator: Margie Orzech Prepress Vendor: S4Carlisle Publishing Services Ninth edition Copyright@ 2019 Wolters Kluwer. Copyright@ 2015 Wolters Kluwer Health. Copyright@ 2008, 2005, 2001 Lippincott Williams & Wilkins. Copyright 1996, 1992, 1989 Williams & Wilkins. All rights reserved. This book is protected by copyright. No part of this book may be reproduced or transmitted in any form or by any means, including as photocopies or scanned-in or other electronic copies, or utilized by any information storage and retrieval system without written permission from the copyright owner, except for brief quotations embodied in critical articles and reviews. Materials appearing in this book prepared by individuals as part of their official duties as U.S. gowmment employEes are not covered by the above-mentioned copyright. To request permission, please contact Wolters Kluwer at Two Commerce Square, 2001 Market Street, Philadelphia, PA 19103, via email [email protected], or via our website at shop.lww.com (products and services). @

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Printed in Mexico Ubrary of Congret11 Cataloglng-in-Publlcatlon Data

Names: Halliday, Nancy L., author. I Chung, Harold M., author. I Preceded by (work): Chung, Kyung Won. Gross anatomy. Title: Gross anatomy I Nancy L Halliday, Harold M. Chung. Other titles: Board review series. Description: Ninth edition. IPhiladelphia : Wolters Kluwer Health, [2020] I Series: BRS I Preceded by Gross anatomy I Kyung Won Chung, Harold M. Chung, Nancy L. Halliday. IIncludes index. Identifiers: LCCN 2018040144 IISBN 9781496385277 (paperback) Subjects: IMESH: Anatomy IExamination Questions IProgrammed Instruction Classification: LCC QM3 l I NLM QS 18.2 IDDC 611-dc23 LC record available at https://lccn.loc.gov/2018040144 This work is provided •as is,• and the publisher disclaims any and all warranties, express or implied, including any warranties as to accuracy, comprehensiveness, or currency of the content of this work. This work is no substitute for individual patient assessment based upon healthcare professionals' examination of each patient and consideration of, among other things, age, weight, gender, current or prior medical conditions, medication history, laboratory data, and other factors unique to the patient. The publisher does not provide medical advice or guidance and this work is merely a reference tool. Healthcare professionals, and not the publisher, are solely responsible for the use of this work including all medical judgments and for any resulting diagnosis and treatments. Given continuous, rapid advances in medical science and health information, independent professional verification of medical diagnoses, indications, appropriate pharmaceutical selections and dosages, and treatment options should be made and healthcare professionals should consult a variety of sources. When prescribing medication, healthcare professionals are advised to consult the product information sheet (the manufacturer's package insert) accompanying each drug to verify, among other things, conditions of use, warnings, and side effects and identify any changes in dosage schedule or contraindications, particularly if the medication to be administered is new, infrequently used, or has a narrow therapeutic range. To the mwdmum extent permitted under applicable law, no responsibility is assumed by the publisher for any injury and/ or damage to persons or property, as a matter of products liability, negligence law or otherwise, or from any reference to or use by any person of this work. shop.lww.com

Special Dedication ta Kyung Wan Chung, PhD

Dr. Kyung Won Chung was the original author of the first eight editions of BRS Gross Anatomy. He was proud of this work, which represented his vast knowledge of anatomy and his passion for teaching. Dr. Nancy Halliday considered Kyung Chung to be a mentor who had a great impact on her development, both as a graduate student and later in her professional career. When invited to be an author for the eighth edition of BRS Gross Anatomy, she considered it a distinct honor and privilege to join her mentor in this, his life's, work. Her desire going forward is to continue his legacy by being a careful steward of his work represented in BRS Gross Anatomy. Dr. Harold Chung grew up with a very close relationship with his father, Kyung Chung. He has collaborated with him since the fourth edition of BRS Gross Anatomy in 2000 in adding to the clinical aspect of the book. As he spent countless hours working with him for the last five editions, he experienced firsthand his father's incredible patience and work ethic, which he hopes he continues with his lessons in his own life, his work, and most importantly his family. We lost a great father, teacher, mentor, and friend with the passing of Kyung Won Chung, PhD.

Dedication

To Frank, my husband and best friend, with deep gratitude for his unwavering support and encouragement. And to my students (past, present, and future) who inspire me. -Nancy L. Halllday To Kathie, my wife, best friend, and soul partner, and to my daughters Kira, Uah, and Maia, for their love, support, and understanding. -Haro'ld M. Chung

vi

Preface

Anatomy is the sc:ience ofstudying and understanding the structure and organization of the body. The art of medicine requires a strong foundation in the basic medical sclen~, and anatomy is a keystone In that foundation. This concise review of human anatomy Is designed for medical, dental, graduate, physlclan associate, nursing, physical therapy, and other health science students. It ls Intended to help students prepare for the United States Medical L!c:enslng BDmlnatlon (USMLE), the NaUonal Board Dental Bnmination, as well as other board examinations for students In health-related professions. It presents the essentlals of hwnan anatomy in the form of condensed descriptions and simple illustrations. The book is concisely outlined with related board-type questions following each sectl.on. It is not intended to substitute for comprehensive textbooks or for co\U'Se syllahl. although the student ma:y find it a useful adjunct to gross anatomy courses. The first chapter reviews general concepts ofgross anatomy. The remaining chapters are organized by anatomic:al regions. Numerous clinical correlations are included in each chapter to emphasize the clinical applications of anatomy. The cranial and autonomic nervous system are separated from the head and neck chapter and are described more extensively with high-quality illustrations to facilitate thorough understanding of cranial and autonomlc nerve functions. The chapter review tests and comprehensive examination at the end of the book consist ofquestions and answers that retlect the guidelines set forth by the National Board of Medical liuminers and the current USMLE format. The questlo.ns reinforce the key information and test basic anatomic knowledge and the students' clinlcal problem-solving ability. The tests are useful in identifying knowledge gaps to guide Independent study. Clear, concise explanations accompany the questions. The questions can be used as a pretest to identify areas of weakness or as a posttest to determine mastery. New to this edition: • Addition of updated and new full-color figures • Updated text and tables • Updated clinical correlations It is the authors' intention to invite feedback comments, constructive criticisms, and valuable suggestions from students and colleagues who choose this book as an aid to learning and teaching basic and

clinical anatomy. Nancy L. HalUday Haro'/d M. Chung

vii

Acknowledgments

We express our sincere thanks to the many students, colleagues, and &iends who have made valuable suggestions that have led to the Improvement of the ninth edition. We are particularly grateful to Rob Jackson, PhD, for providing his invaluable criticism or the text as well as for hls copyediting during the preparation phase of this current edition. OUr grateful appreciation Is also extended to John M. Chung, MD, for prov!d.lng hls invaluable crltlcfam of the text and clinically oriented test questions as well as for his copyediting during the preparation phases of previous editions. We are also grateful to Daniel O'Donoghue, PhD, for his encouragement, constructive criticism of the text and clinical notes, and helpful suggestions during the preparation of1his current edition, as well as previous editions. Finally, we greatly appreciate and enjoy the privilege ofworking with the Wolters Kluwer staff, including Crystal Tu.ylor; Acquisitions Editor; Kerry McShane, Editorial Coordinator; Andrea Vosburgh, Development Editor; JeDDifer Clements, Art Director; Jeethu Abraham, Senior Project Manager; and Alicia Jackson, Senior Produ.c:tion Project Manager. We thank the staff for their constant guidance, enthusiasm, and unfailing support throughout the preparation, production, and completion of this new edition.

viii

Contents

Preface vil Acknowledgments viii

1. INTRODUCTION

1

Skeletal Sptem 1 I. Bones 1 II. Joints 2 Muscular System 4 I. Muscle 4 II. Structures Associated With Skeletal Muscles 5

Nervous System 5 I. Nervous System 5 II. Neurons 6 Ill. Central Nervous System 7 IV. Peripheral Nervous System 7 V. Autonomic Nervous System 9 Circuletory System 11 I. Vascular System 11 II. Lymphatic System 12 Organ Systems 13 I. Digestive System 13 II. Respiratory System 14 Ill. Urinary System 14 IV. Reproductive System 14 V. Endocrine System 15 VI. Integu:mentary System 15 High-Yield Topics 15 Review Test 18

2.

BACK

22

Vertebral Column 22. I. General Characteristics 22 II. Typical Vertebra 24 Ill. Intervertebral Disks 26 IV. Regional Characteristics of Vertebrae 27 V. Ligaments of the Vertebral Column 29 VI. Vertebral Venous System 30 ix

x

Contents

Structures of the Back 31 I. Superficial Back 31 II. Structures of the Deep Back 33 Ill. Suboccipital Region 34

Spinal Cord and Associated Structures 3& I. Spinal Cord 36

II. Ill. IV. V. VI.

Spinal Nerves 37 Meninges 38 Structures Associated With the Spinal Cord 40 Dermatome, Myotome, and Sclerotome 41 Development of Back Structures 42 High-Yield Topics 42

Review Test 45

3.

THORAX Thoracic Wall 52 I. Skeleton of the Thorax 52

II. Ill. IV. V. VI.

Articulations of the Thorax 54 Breasts and Mammary Glands 55 Muscles of the Thoracic Wall 55 Nerves and Blood Vessels of the Thoracic Wall 55 Lymphatic Drainage of the Thorax 56 VII. Thymus 56 VIII. Diaphragm and Its Openings 57 Mediastinum, Pleura, and Organs of Respiration 57 I. Mediastinum 57

II. Ill. IV. V. VI.

Trachea and Bronchi 58 Pleurae and Pleural Cavities 59 Lungs 62 Respiration 64 Lymphatic Vessels of the Lung 65 VII. Blood Vessels of the Lung 65 VIII. Nerve Supply to the Lung 67 IX. Development of the Respiratory System 68 Pericardium and Heart 69 I. Pericardium 69

II. Ill. IV. V. VI.

Heart 70 Great Vessels 79 Development of the Heart 80 Development of the Arterial System 83 Development of the Venous System 84 VII. Fetal Circulation 84 Structures in the Posterior Mediastinum 85 I. Esophagus 85

II. Blood Vessels and Lymphatic Vessels 86 Ill. Autonomic Nervous System in the Thorax 89 High-Yield Topics 91 Review Test 97

52

Contents

xi

4. ABDOMEN

109

Anterior Abdominal Wall 109 I. Abdomen 109 II. Muscles of the Anterior Abdominal Wall llO Ill. Fasciae and Ligaments of the Anterior Abdominal Wall llO IV. Inguinal Region 112 v. Spennatic Cord, Scrotum, and Testis ll3 VI. Inner Surface of the Anterior Abdominal Wall 114 VII. Nerves of the Anterior Abdominal Wall 115 VIII. Lymphatic Drainage of the Anterior Abdominal Wall 116 IX. Blood Vessels of the Anterior Abdominal Wall ll6 Paritonaum and Paritonaal Cavity 117 I. Peritonewn ll 7 II. Peritoneal Reflections 117 Ill. Peritoneal Cavity 119 Gastrointestinal (GI) Viscera 120 I. Esophagus (Abdominal Portion) 120 II. Stomach 121 Ill. Small Intestine 123 IV. Large Intestine 124 V. Accessory Organs of the Digestive System VI. Spleen 130 VII. Development of Digestive System 131 VIII. Celiac and Mesenteric Arteries 133 IX. Hepatic Portal Venous System 137

126

Retroperitoneal Viscera. Diaphragm. and Posterior Abdominal Wall 140 I. Kidney, Ureter, and Suprarenal Gland 140 II. Development of Kidney, Urinary Bladder, and Suprarenal Gland Ill. Posterior Abdominal Blood Vessels and Lymphatics 144 IV. Nerves of the Posterior Abdominal Wall 145 V. The Diaphragm and Its Openings 148 VI. Muscles of the Posterior Abdominal Wall 150 High-Yield Topics 150 Raviaw last 156

5.

PERINEUM AND PELVIS Parineal Ragion 170 I. Perineum 170 II. Urogenital Triangle 170 Ill. Anal Triangle 174 IV. External Genitalia and Associated Structures V. Nerve Supply of the Perinea! Region 178 VI. Blood Supply of the Perinea! Region 180 Palvis I. II. Ill.

181 BonyPelvis 181 Joints of the Pelvis 184 Pelvic Diaphragm 184

143

170

175

xii

Contents

IV. Ligaments or Folds and Pouches of the Pelvis 184 V. Ureter and Urinary Bladder 186 VI. Male Genital Organs 190 VII. Female Genital Organs 194 VIII. Rectum and Anal Canal 197 IX. Blood Vessels of the Pelvis 199 X. Nerve Supply to the Pelvis 202 XI. Development of the Lower Gastrointestinal Tract and Urinary Organs 203 XII. Development of the Reproductive System 205 High-Yield Topics 205 Review Test 211

6.

LOWER LIMB

224

Bonas of the Lower Limb 224

I. Hip (Coxal) Bone (Os Coxa)

224 226 Ill. Bones of the Ankle and Foot 228 II. Bones of the Thigh and Leg

Joints and Ligaments of the Lower Limb 230

I. Hip (Coxal) Joint 230 232 Ill. Tibiofibular Joints 236 IV. Ankle (Talocrural) Joint 236 V. TarsalJoints 237 II. Knee Joint

Cutaneous Nerves, Superficial Veins, and Lymphatics 238

I. Cutaneous Nerves of the Lower Limb II. Superficial Veins of the Lower Llmb

238 240

Ill. Lymphatics of the Lower Llmb 240 Muscles of the Lower Limb 241

I. Muscles of the Gluteal Region

241 242 Muscles of the Anterior and Medial Thigh 243 Anterior and Lateral Muscles of the Leg 245 Posterior Muscles of the Leg 246 Muscles of the Foot 247

II. Posterior Muscles of the Thigh

Ill. IV. V. VI.

Nerves of the Lower Limb 250

I. Branches of the Lumbar and Sacral Plexuses Blood Vessels of the Lower Limb 254

I. Arteries of the Lower Limb

254 258 Ill. Development of the Lower Limb 259 High-Yield Topics 259 Summary 263 II. Deep Veins of the Lower Llmb

Review Test 265

250

Contents

7.

UPPER LIMB

280

Bonas and Joints of Iha Upper Limb

I. II. Ill. IV.

xiii

ZBO

Bones of the Shoulder Girdle 280 Bones of the Ann and Forearm 282 Bones of the Hand 285 Joints and Ligaments of the Upper Limb

286

Cutaneous Nerves. Superficial Veins. and Lymphatics ZBB I. Cutaneous Nerves of the Upper Limb 288

II. Superficial Veins of the Upper Limb 290 Ill. Superficial Lymphatics of the Upper Limb 291 Axilla and Breast 291 I. Fasciae of the Axilla and Pectoral Regions

II. Axilla (Armpit) 292 Ill. Breast and Mammary Gland

291

295

Muscles of the Upper Limb 298 I. Muscles of the Pectoral Region and Axilla

298

II. Muscles of the Shoulder Region 299 Ill. Muscles of the Arm and Forearm 301 IV. Muscles of the Hand 303 Nerves of the Upper Limb 308 I. Brachia! Plexus 308 II. Nerves of the Arm, Forearm, and Hand

311

Ill. Functional Components of the Peripheral Upper Limb Nerves 314 315 Branches of the Subclavian Artery Axillary Artery 315 BrachialArtery 316 Radial Artery 317 Ulnar Artery 318 Veins of the Upper Limb 319 Development of the Limbs 320 High-Yield Topics 321 Summary 323

Blood Vassals of tha Upper Limb

I. II. Ill. IV. V. VI. VII.

315

Review Test '321

8.

345

HEAD AND NECK Structures of tha Nack 345

I. II. Ill. IV. V.

Major Divisions and Bones Muscles 347 Nerves 348 Blood Vessels 350 Lymphatics 356

345

xiv

Contents Deep Neck and Prevertebral Region 357 I. Deep Structures of the Neck 357 II. Deep Cervical Fasciae 360 Ill. Prevertebral or Deep Neck Muscles 362 IV. Development of Thyroid and Parathyroid Gland 362

Face and Scalp 363 I. Muscles of Facial Expression

363

II. Nerve Supply to the Face and Scalp Ill. Blood Vessels of the Face and Scalp IV. Scalp 368

364 366

Temporal and lnfratamporal Fossaa 369 I. Introduction 369

II. Ill. IV. V. VI.

Muscles of Mastication 371 Nerves of the Infratemporal Region 372 Blood Vessels of the Infratemporal Region 373 Parotid Gland 375 Joints and Llgaments of the Infratemporal Region

Skull and Cranial Cavity 377 I. Skull 377

II. Ill. IV. V. VI. VII.

VIII. IX. X.

Bones of the Cranium 377 Sutures of the Skull 378 Foramina in the Skull 379 Structures in the Cranial Fossae 382 Meninges of the Brain 383 Cranial Venous Channels 385 Blood Supply of the Brain 386 Nerves of the Head and Neck 388 Development of the Skull 388

Orbit 389 I. Bony Orbit

389 Nerves 391 Blood Vessels 393 Muscles of Eye Movement 395 Lacrimal Apparatus 397 Eyeball 398 VII. Development of the Eye 401 II. Ill. IV. V. VI.

Oral Cavily and Palate 401 I. Oral Cavity 401 II. Palate 402

Ill. IV. V. VI.

Tongue 404 Teeth and Gums or Gingivae 405 Salivary Glands 407 Development of the Palate 408 VII. Development of the Tongue 408 VIII. Development of Teeth 408 IX. Development of Salivary Glands 409

376

Contents Pharynx and Tonsils 409

I. II. Ill. IV. V. VI. VII. VIII.

Pharynx 409 Subdivisions of the Pharynx 409 Innervation and Blood Supply of the Pharynx Muscles of the Pharynx 411 Swallowing (Deglutition) 412 Tonsils 412 Fascia and Space of the Pharynx 413 Pharyngeal (Branchial) Apparatus 414

410

Nasal Cavity and Paranasal Sinuses 415

I. II. Ill. IV. V. VI.

Nasal Cavity 415 Subdivisions and Mucous Membranes 417 Blood Supply to the Nasal Cavity 417 Nerve Supply to the Nasal Cavity 418 Paranasal Sinuses 418 Development of the Nasal Cavity 419

Plerygopalatine Fossa 420

I. Boundaries and Openings 420 II. Contents 420 Larynx 422

I. II. Ill. IV. V. VI. VII.

Introduction 422 Cartilages 422 Ligaments of the Larynx 423 Cavities and Folds 424 Muscles 425 Innervation 426 Development of the Larynx 427

Ear 427

I. II. Ill. IV. V.

External Ear 427 Middle Ear 429 Inner Ear 432 Hearing and Equilibrium 433 Development of the Ear 433 High-Yield Topics 434

Review Test 446

9.

CRANIAL AND AUTONOMIC NERVES I. Cranial Nerves 463 II. Autonomic Nerves of the Head High-Yield Topics 480 Review Test 483

Comprehensive Examination Index 510

489

476

463

xv

Introduction

Gross anatomy can be approached through the study of body systems, by regions, or through clinically significant anatomic concepts. Systemic anatomy relates structure to function by organ systems, such as the respiratory, digestive, or reproductive systems. Regional anatomy is based on regions and deals with all organs and structural and functional relationships in identified parts of the body, such as the thorax and abdomen, with emphasis on skeletal elements, muscles, organs, ner es, and blood vessels. Anatomy is best when reinforced by relating it to clinical medicine, and thus clinical anatomy emphasizes the practical application of anatomic knowledge to the solution of cli ical prnolems. Long-term, this has a real pertinence to the practice of medicine. In this introductory eli~ter, He systemic approach to the study of anatomy is used. In subsequent chapters, the regional and clinical approaches to anatomy are used. Many injuries and diseases involve specific body regions, an ost dissections and obviously surgical procedures are performed by region. Thus, clinica correlations are presented throughout the text to reinforce the basic concepts.

SKELETAL SYSTEM

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Consists of the axial skeleton (bones of the head, vertebral column, ribs, and sternum) and the appendicular skeleton (bones ofln:e extremities).

I. BONES

■

Are classified as connective tissue consisting of cells (osteocytes) embedded in a matrix of ground substance and col agen fibers in a specific structure that is calcified. Bones have a superficial thin layer of compact bone around a central mass of spongy bone, and internal soft tissue, the marrow, where blood progenitor cells are found. Serve as a reservoir for calcium and phosphorus in addition to their role as biomechanical levers on which muscles act to produce the movements at joints. Are classified into long, short, flat, irregular, and sesamoid bones. According to their developmental history, they are also categorized into endochondral and membranous bones.

A. Long bones ■ Include the humerus, radius, ulna, femur, tibia, fibula, metacarpals, and phalanges. Develop by replacement ofhyaline cartilage plate (endochondral ossification). ■ Have a shaft (diaphysis) and two ends (epiphyses). The metaphysis is a part of the diaphysis adjacent to the epiphyses. 1. Diaphysis Forms the shaft (central region) and is composed of a thick tube of compact bone that encloses the marrow cavity.

2

BRS Graa Allatamy

2. Mltlphysis • Is the broadened region of the diaphysls adjacent to the epiphysis. Growth plates are located between the metaphysis and epiphysis during bone development. 3. Epiphyses • Are expanded articular ends, separated from the shaft by the epiphyseal plate during bone growth and composed ofa spongy bona surrounded by a thin layer ofcompact bona.

B. Short bones • Include the carpal and tarsal bones and are approximately cuboid shaped. • Are composed ofspongy bone and marrow surrounded by a thin outer layer of compact bone.

C. Ralbonas • Include the ribs, sternum, scapulae, and bones of the cranial vault • Consist of two layers of compact bona enclosing spongy bona with a marrow space (diploi). • Have articular surfaces that are covered with ftbrocartilage and grow by the replacement of connective tissue. D. lrragular bones

• Include bones of mmd shapes, such as bones of the face, vertebrae, and com. • Contain mostly spongy bona enveloped by a thin outer layer of compact bone.

E. S11amoid bones • Develop in certain tendons and reduce friction on the tendon and shift the mechanical advantage, thus protecting it from excessive wear. • Are commonly found where certain tendons cross synovial articulations at the ends of long bones in the limbs, as in the wrist (i.e., pisiform) and the knee (i.e., patella).

CLINICAL CORRELATES

Dsleoblasts synthesize new bone, and osleoclasls function in resorption (break down bone matrix and release calcium and minerals}. Bone remodeling is a normal metabolic process and includes bath processes. Parathyroid hormone causes mobilization of calcium by promoting bona resorption, whereas calcitonin and bisphosphonatas suppress mobilization of calcium from bone. Ostaoid is the organic matrix of bone prior to calcification. Osleomyelilis is an infection of the bone wittl organisms such as Staphylococcus or StnlptDcaccus (from penetrating traum al, Salmons/la, or tuberculosis (Pott disease). Oslaomalacia is a gradual softening of a bone ca used by mechanical forces or metabolic issues such as failure of the bone to calcify because of lack of vitamin Dor renal wbular dysfunction. Ostaopenia is a decreased calcification of bone or a reduced bone mass caused by inadequate osteoid synthesis. Osteopenia is an age-related disorder characterized by decreased bone mass and increased susceptibility to pathologic fractures (ostaoporasis) of the hip, vertebra, and wrist. When bone resorption outpaces bone formation during bone remodeling, the bones weaken. Normal bone metabolism is characterized by constant cycles of resorption and formation (remodeling) to maintain the concentration of calcium and phosphate in the extracellular fluid. The pathologic signs of osteoporosis are vertebral compression, loss of body height. development of kyphosis, and hip fracture. Oslaapetrosis is a disease that makes bones abnormally dense and prone to fracture, because of defective resorption of bone.

II. JOINTS • Are places of union between two or more bones. • Are innervated as follows: the nerve supplying a joint also supplies the muscles that move the joint

and the skin covering the insertion of such muscles (Hillan law). • Are classified on the basis of their structural features into fibrous, cartilaginous, and synovial types.

l!1ltmJll

Introduction

3

A. Fibrous joints (synarthroses) Are joined by fibrous tissue, have no joint cavities, and permit little movement.

1. Sutures Are connected by fibrous connective tissue, such as the fibrous continuities between the

flat bones of the skull.

2. Syndasmoses Are connected by dense fibrous connective tissue.

Occur as the inferior tibiofibular syndesmoses and tympanostapedial syndesmoses (between the foot plate of the stapes and the oval window in the middle ear).

B. Cartilaginous joints Are united by carti Iage and have no joint cavity. 1. Primary cartilaginous joints (synchondrosas) Are united by hyali ne carti Iage and permit little to no movement but allow for growth in length during childhood and adolescence. Include epiphyseal cartilage plates (the union between the epiphysis and the diaphysis of a growing bone) and spheno-occipital and manubriosternal synchondroses.

2. Secondary cartilaginous joints (symphyses) Are joined by tibrocartilage and are slightly movable joints. Are all located in the median plane and include the pubic symphysis and the interver-

tebral disks.

C. Synovial (diarthrodial) joints Are found between two separate skeletal elements and permit certain degrees of movement according to the shape of the articulation and/ or the type of movement. Are characterized by four structural features: joint cavity or space, articular (hyaline) cartilage, synovial membrane, which produces synovial fluid, and articular capsule.

1. Plane (gliding) joints Have flat articular surfaces and allow a simple back-and-forth gliding or sliding of one bone over the other. Occur in the proximal tibiofibular, intertarsal, intercarpal, intennetacarpal, carpometacarpal, stemoclavicular, and acromioclavicular joints.

2. Hinge (ginglymus) joints Resemble door hinges and allow only flexion and extension. Occur in the elbow, ankle, and interphalangeal joints.

3. Pivot (trochoid) joints Are formed by a central bony pivot turning within a bony ring and allow only rotation

(movement around a single longitudinal axis). Occur in the superior and inferior radioulnar joints and in the atlantoaxial joint.

4. Condylar (ellipsoidal) joints Have two convex condyles articulating with two concave condyles. (The shape of the articulation is ellipsoidal.) Allow flexion and extension and occur in the wrist (radiocarpal), metacarpophalangeal, knee (tibiofemoral), and atlanto-occipital joints.

5. Saddle (sellar) joints Resemble the shape of a horse's saddle and allowtlexion/extension, abduction/adduction, and circumduction, but no axial rotation. Occur in the carpometacarpal joint of the thumb and between the femur and patella.

&. Ball-and-socket (spheroidal or cotyloidl joints Are formed by the reception of a globular (ball-like) head into a cup-shaped cavity and allow movement in many directions. Allow tlexion and extension, abduction and adduction, medial and lateral rotations, and circumduction and occur in the shoulder and hip joints.

4

BRS Grass Anatomy

CLINICAL

Osteoarthritis is a degenerative joint disease driven by inflammatory mediators produced by bone cells, chondrocytes, and synovial membranes. Osteoartllritis results in the degeneration of the articular cartilage and osseous outgrowth at the synovial margins. There are a number af predisposing factors including injury and obesity. It commonly affects the hands, fingers, hips, knees, feet, and spine and is accompanied by pain and stiffness. Rlleumatoid artllritis is an inflammatory disease driven by immunologic attack primarily of the joints. Antibodies directed at the synovia I membranes and articular structures lead to deformities and disability. While no cure is known, there are several disease-modifying options. The mast common symptoms are joint swelling, stiffness, and pain. Gaut is a painful fonn of crystalline arthritis end is caused by uric acid crystel deposits into joint spaces from the blood. These deposits cause inflammation and pain, heat, redness, stiffness, tenderness, and swelling of the first toe or thumb, characteristically, but can impact other joints as well. P11udogout has similar clinical presentation but is related to calcium crystal deposits usually after chronic injury.

CORRElATES

MUSCULAR SYSTEM I. MUSCLE • Consists predominantly of cantnctile cells, produces the moY&ments ofvarious parts of the body by contraction, and occurs in three types:

A. Skeletal muscle Is considered voluntary and has a striated histologic structure to its component myofibrils. Makes up approximately 40% of the total body mass and functions to produce movement of the body, generate body heat, and maintain body posture. Has two attachments: an origin, which is usually defined by a more fixed and proximal attachment, and an insertion, which is typically defined as the more movable and distal attachment. Is enclosed by fascia, the epimysium, which is a thin but tough layer of connective tissue surrounding the entire muscle. Within the muscle, smaller bundles of muscle fibers are surrounded by parimysium. Each individual muscle fiber ls enclosed by andomysium.

CLINICAL

Amyatrophic lataral sclerosis (ALS, or Lou Gehrig disease) is a disease that attacks the motor neurons that control voluntary muscles. The muscles weaken and atrophy. Ultimately, ttie brain is unable to control voluntary movement of ttie arms, legs, and body, and patients lose the ability to breath, swallow, and speak. The earliest symptoms may include cramping, twitching, and muscle weakness.

CORRELATES

B. Cardiac muscle Is striated muscle fibers found in the wall of the heart, the myocardium. Cardiac muscle contractions are autonomous, but the rate can be modulated by the autonomic nervous system (ANS). • Includes subendocardial specialized myocardial fibers that form the cardiac conducting system.

C. Smooth muscle Is involuntary and nonstriated and found in the walls of organs and blood vessels. Jn the walls ofhollow organs, smooth muscle is arranged in two layers, circular and longitudinal, that allow rhythmic contractions called peristaltic waves in the walls of the gastrointestinal (GI) tract, uterine tubes, ureters, and other organs. Is innervated by the ANS, regulating the size of the lumen of a tubular structure.

l3JIEtlij Introduction

5

II. STRUCTURES ASSOCIATED WITH SKELETAL MUSCLES A. Tendons Are fibrous bands of dense connective tis.sue that conn act muscl&1 ID ban&1 or cartilage. Are supplied by sensory fibers extending from muscle nerves.

B. Ligaments Are fibrous bands that connect bones ID bones or cartilage (the term is also used for folds of peritoneum serving to support visceral structures).

C. R1ph1 • Is a seam of union of symmetrical structures by a fibrous or tendinous band, such as the pterygomandibular, pharyngeal, and scrotal raphes.

D. Aponauro111 • Are flat fibrous tendons of attachment that serve as the means of origin or insertion of a muscle.

E. Retinaculum • Is a fibrous thickeDlng of the deep fascia that stabilizes tendons and neurovascular st:ru.ctures as they cross a joint in the distal limbs.

F. Bursae • Are fluid-filled flattened sacs of synovial membrane that facilitate movement by minimizing friction between a bony joint and the surrounding soft ti8Sue, such as skin, muscles, ligaments.

G. Synovial tendon sheaths Are synovial fluid-filled tubul1r ucs around muscle tendons that facilitate movement by reducing friction as tendons pass distally into the limbs.

H. Fascia Is a fibro!D sheet that envelops the body under the skin and iIIYests the muscles and may limit the spread of pus and exttavasated Ouids, such as urine and blood. 1. Superficial fascia • Is a fatty connective tissue between the dermis and the deep muscular fascia and is considered the hypodermis with fat, cumneous vessels, nerves, lymphatics, and glands. In a few locations, there may be a membranous daap layer al superficial fascia (abdominal wall). Z. Daap fascia • Is a sheet offibrous tissue that invests Iha mu1cl11 and helps support them by serving as an elatltic sheath or stocking. • Provides origins or insertions for muscles, forms fibrous sheaths or retinacula for tendons, and forms potential pathways for spread of infection or extravasation of fluids.

NERVOUS SYSTEM I. NERVOUS SYSTEM Is divided anatomically into the central nervous system (CNS), consisting of the brain and spinal cord, and the perlpheral nervous system (PNS), consisting of 12 pairs of cranlal nerves and 31 pairs

of spinal nerves and their associated ganglia. Is divided functionally into the somatic nervous system, which controls primarily voluntary activities, and the visceral (autonomic) nervous system, which controls primarily involuntary activities. Is composed of neurons and neuroglia (non-neuronal cells such as astrocytes, oligodendrocytes, and microglia} and controls and integrates the body activity.

&

BRS Graa Allatamy

II. NEURONS • Are the structural and functional units of the nervous system (neuron doctrine). • Are specialized for the reception, integration, transformation, and transmission of information.

A. Componentl of neurons

1. Collections of neuronal cell bodin are termed gray matter ornuclei in the CNS. and collections of neuronal cell bodies are called ganglia in the PNS.

Z. Dendrites (dendron means "tree") are highly branched extensions from the cell body that carry hnpul.ses from local circuitry toward the cell body. 3. Amos are usually single and long, have fewer branches (collaterals), and carry impulses away from the cell body.

B. Classification of neurons based on 1hap1 1. Unipolar (puudounipolar) neurons • Have one process, which divides into a branch directed at the CNS and a peripheral branch that brings information toward the cell body from peripheral receptors. • Are called pseudounipolar because they were originally bipolar, but their two processes fuse during development to form a single process that bifurcates at a distance from the cell body. • Are sensory neurons of the PNS and found in spinal and cranial nerve ganglia.

Z. Bipolar neurons • Have two proce11H: one proximal (CNS) and the other Is distal (PNS). • Are found in association with some of the special senses like olfaction, vision, and hearing.

3. Multipolar neurons Have nveral dendrites and one axon and are most common in the CNS (e.g., motor cells in the anterior and lateral horns of the spinal cord, autonomlc ganglion cells).

C. Clusters of nerve call bodies • A ganglion is a collection of neuron cell bodies outside the CNS {e.g., dorsal root ganglion, autonomic ganglia).

• A collection of neuron cell bodies within the CNS is called a nucleus. An exception is the basal ganglia, which is a group of subcortical nuclei.

D. Other components of the nervous tissuesllystem 1. Cells that support neurons • Include Schwann cells and satellite cells in the PNS. Are called neuroglia in the CNS and are composed mainly of three types: astrocytes; oligodendrocy181, which play a role in myelin formation and transport ofmaterial to neurons; and microglia, which phagocytose waste products of nerve tissue. Z. Myalin • Is the membrane-wrapped sheath around certain nerve axons. • Is formed by Schwann cells in the PNS and oligodendrocytes in the CNS. 3. Synapses • Are the sites of functional contact of an u:on terminal of one neuron with the cell body or dendrites of another neuron, or an effector (mu11cle and gland) cell, or a sensory

receptor cell. • Are classified by the site of contact as uodendrlttc, axoaxonlc, or axosomattc.

• Are the sites of impulse transmission commonly from the ax.on terminals (presynaptic elements) to the plasma membranes (postsynaptic elements) ofthe receiving cell via a neural transmitter across the synaptic cleft.

l3JIEtlij Introduction

1

Ill. CENTRAL NERVOUS SYSTEM A. Brain Is enclosed within the cranlal vault. Ha.s a cortex, which is the 011tar part ofthe cerebral hemispheres, composed of gray mattar. This matter consists largely of the nerve call bodies, dendrites, and neuroglla. • Has an interior part composed ofwhite matter, which consists largely of exons forming tracts or pathways, and ventricles, which are filled with cerebrospinal fluid (CSP).

B. Spinal cord Is cylindrical, occupies approximately the upper two-thirds ofthe vertebral canal, and is enveloped by the meninges. • Has cervical and lumbar enlargements for the nerve supply of the upper and lower limbs, reapectively. • Hea centrally located gray matter and peripherally located white matter. • The spinal cord is shorter than the vertebral canal, ending between L1 and L2vertebral level because the cord grows more slowly than the surrounding vertebral column during fetal development The conical end of the spinal cord is called the conus m1dullari1 and is located near the level of L2 (or between L1 and L2) in the adult and at the level of13 In the newborn. The conus medullaris attaches caudally to the coccyx through the sacral canal via the filum terminale located among the roots of the cauda equina.

C. Meningas Comist of three layers of connective tissue membranes lpia, arachnoid, and dun mater) that surround and protect the brain and the spinal cord. Contain the 111barachnoid space, which is the interval between the arachnoid and pia mater, filled with CSR • The pia mater carries the vascular supply to the surface of the brain and spinal cord and is intimately invested with the external surfaces of these.

D. C1rebrospinal fluid • Is produced by vascular choroid plexuses in the lateral ventricles, third ventricle, and fourth ventricle of the brain. • Flows through the ventricles to drain into the subarachnoid space from the fourth ventricle.

CUNICAL

Multiple sclerosis IMS) is an autoimmune destruction of myelin found in the optic nerve, brain, brainstem, and spinal cord, leading to sansory disorders and muscle weakness. Signs and symptoms include numbness or tingling, visual disturbances because of optic nerve involvement, cognitive impairments, muscle weakness, difficulty with coordination and balance, slurred speech, bladder incontinence, fatigue, depression, and memory problems. MS is seen in individuals who have a genetic predisposition and some viral-associated trigger of autoimmunity. Destruction of myelin disrupting 'the conduction of nerve signals along the axons. MS affects women more often 'than men.

CORRELATES

IV. PERIPHERAL NERVOUS SYSTEM A. Cranial n11Y11 Consist of1Z pairs and are connected to the brain and brainstem. Have motor fibers with cell bodies located within the CNS and sensory fibers with cell bodies that form sensory ganglia located outllide the CNS. • Emerge from the ventral aspect of the brain (except for the trochlear nerve, or cranial nerve IV). Contain different functional components based on the cranial nerve functions.

8

BRS Gross Anatomy

B. Spinal nerves (Figure 1.1) Consist of31 pairs: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal. Are formed from dorsal and ventral roots; each dorsal root has a ganglion that is associated with each intervertebral foramen. Are connected with the sympathetic chain ganglia by white (Tl-L2) and gray (all spinal nerves)

rami (communicantes). Contain sensory fibers with cell bodies in the dorsal root ganglion for somatic and visceral sensations. Contain motor fibers with cell bodies in the anterior horn of all levels of the spinal cord for stimulation of skeletal muscles and visceral motor fibers from cell bodies in the lateral horn of the spinal cord (Tl through 12, S2, 83, and S4). Branch into venlral primary rami to supply for the body wall through major plexuses (i.e., cervical, brachia!, and lumbosacral) and intercostal nerves. Branch into the dorsal primary rami to innervate the skin and deep muscles of the back.

C. Functional components in peripheral nerves (Figures 1.2 and 1.3) 1. Somatic afferent fibers (formerly general somatic afferent) Transmit pain, temperature, touch, and proprioception from peripheral receptors or the skin of the body to the CNS.

2. Somatic efferent fibers (formerly general somatic efferent) Carry motor impulses from CNS motoneurons to the skeletal muscles of the body.

3. Visceral afferent fibers (fonnerly general visceral afferent) Convey sensory impulses from visceral organs and blood vessels to the CNS.

4. Visceral efferent fibers (autonomic nerves, formerly general visceral efferent) Transmit motor impulses from the CNS through a peripheral autonomic ganglion to smooth muscle of the viscera or blood vessels, cardiac muscle, and glandular tissues.

5. Special sensory fibers (formerly special somatic afferent and special visceral afferent) Convey special sensory impulses of the eye and ear for vision, hearing, and equilibration through cranial nerves to the CNS.

Lateral branch

..&'~-=:::"'iMuscular branch

Sympathetic ganglion Lateral cutaneous branch

Anterior Medial branch

Lateral branch

FIGURE 1.1. Typical spinal nerve (anterior, ventral; posterior, dorsaO.

l3JIEtlij

=oJ

Introduction

9

Dorsal root Splnal (donial root) gangllon

lntemeuron

Spinal nel'VB

7~ ---,~JJ,,_=..:~;-

"""'--f::1~ _.LSkin (receptor) ----- Skele1BI muscle Splnal cord- \ jl__.:; ~~~ I (effector) 7 Somatic Ventral primary ramus Ventral root efferent fiber --J vJ White. ramus

\ 'J '\\.

Gray rarnus

rCJ

_La.

Sympathetic chain ganglion

RGURE 1.2. Somatic affarant and afferent ne NBS.

FIGURE U. Viscaral efferent (autonomic) and afferent nerves.

Transmit senses ofsmell from the nasal cavity and taste sensations from the oral cavity through cranial nerves to the CNS.

6. Spacial visceral efferent fiber1 (old teminology) Conduct motor impulses to the muscles that develop in usociation with one ofthe branchiomeric arches: first arch-muscles for mastication; second arch-muscles for facial expression; third arch-stylopheryngeus muscle; fourth arch-palatal and pharyngeal muscles for elevation of the pharynx; or sixth arch-movement of the larym. • There is no fifth arch. This scheme ls not used as widely as !twas previouslyand will not show up on board examinations.

V. AUTONOMIC NERVOUS SYSTEM Is responsible for the motor innervation of smooth muscle, cardiac muscle, and glands {Table 1.1).

It is divided into the sympathetic (thoracolumbar outftow), p1n1sympathetic (craniosacral outftow), and all'IBric divisions. ls composed of two neurons, pregangllonic and postgangllon!c, which are visceral efferent neurons. It has cholinergic fibers (sympathetic pregangllonic, parasympathetic preganglionic, and

BRS Gross Anatomy

10 t

a b I e

1.1

Functions of Autonomic Nerves

Organs

Sympathetic Nerve

Eyes

Dilates pupil

Lacrimal gland Salivary gland Sweat gland Blood vessels Heart Bronchi GI tract Liver Su prarenal medulla Kidney Urinary bladder Genita I organs

Par1symp1thetic Nerve

Constricts pupil; contracts cilia ry muscle to thicken lens Slightly reduces secretion Promotes secretion Reduces secretion and mare viscid Increases secretion and watery Stimulates secretion No effect Constricts No affect In creases rate and ventricular contraction; dilates Decreases rate and ventricular contraction; coronary vessels constricts coronary vessels Dilates lumen; reduces bronc hial secretion Constricts lumen; promotes secretion In hibits motility and secretion; constricts Stimulates motility and secretion; relaxes sphincters sphincters Promotes glycogen breakdown Promotes glycogen formation and bile secretion Secretes epinephrine and no re pine phrine No affect Reduces urine formation by constriction of renal Mey cause vasodilation of renal vascular bed vessels Relaxes sphincter vesicae; contracts detrusor Contracts sphincter vesicaa muscle, during urination Causes vasacanstrictian and the propulsion of Causes vasadilatian and erection; relaxes uterus ejaculation; sphincter vesicae is contracted to prevent retrograde ejaculation; contracts uterus

parasympathetic postganglionic) and adrenergic fibers (sympathetic postganglionic) except those to sweat glands (cholinergic). Praganglionic neuron cell bodies are located in Ille CNS, whereas postganglionic neuron cell bodies are in ganglia in the PNS.

A. Sympathetic nerve fibers (see Figure 1.3) Have preganglionic nerve cell bodies that are located in the lateral horn ofthe thoracic and upper lumbar levels (12 or Ll-1..3) of the spinal cord. Have preganglionic fibers that pass out of the spinal cord through ventral roots, spinal nerves, and then enterthe white rami (communicantes). Preganglionic fibers enter adjacent sympathetic chain ganglia, where they synapse or travel up or down the chain to synapse in remote chain ganglia for the autonomics of the body wall. Postganglionic fiben from the neurons in the chain ganglia return to spinal nerves byway of gray rami and supply the skin with secretory fibers to sweat glands, motor fibers to smooth muscles of the hair follicles (arrectores pilorum), and vasomotor fibers to the blood vessels of the body wall. Alternatively, preganglionic fibers run ventrally through to the splanchnic nerves to synapse in praaortic (collateral) ganglia. Postganglionic fibers from the preaortic ganglia travel with arteries to innervate the viscera of the abdomen and pelvis. Sympathetics function primarily in emergencies or catabolism (energy consumption), preparing individuals for fight or flight, and thus increase the heart rate, inhibit GI motility and secretion, and dilate pupils and bronchial lumen. They liberate norepinephrine (except sweat glands) and are classified as adrenergic.

B. Parasympallletic nerve fibers Comprise the preganglionic fibers that arise from the brainstem (cranial nerves III, VII, IX, and X) and the second, third, and fourth sacral spinal segments. Are distributed to the internal organs and walls of the viscera and glands of the digestive and respiratory systems but not to the skin or body wall and limbs. Decrease the heart rate, increase GI peristalsis, and stimulate secretory activity.

l3JIEtlij Introduction

11

• Parasympathetics function primarily in homeostasis or anabolism (energy conservation), tending to promote quiet and orderly processes of the body. They liberate acetylchollne and are classified as chollnergic.

C. Entaric division Consists of a complexweb of interconnecting neurons with multiple different neurotransmitters located in the walls of the GI tract. • The enteric ganglia are parasympathetic postganglionic neuron cell bodies and plexuses of the GI tract that include the classically described m.yenteric (Auerbach} and submucosal (Meissner} plexuses. • Plays an important role in the control of GI motility and secretion.

CIRCULATORY SYSTEM I. VASCULAR SYSTEM • Functions to circulate vital materials such as oxygen, nutrients to the tissues, and waste products

to the kidneys. liver, and lungs. • Other circulating elements are carbon dioxide, hormones, antibodies, and cells involved in inflammation, immunology, and wound healing. Consists of the heart and va111l1 (arteries, capillaries, and veins) that transport blood through all parts of the body. • Also includes the lymphatic v888811, a set of channels that begin in the tissue spaces and return tissue fluid to the bloodstream.

A. Circulatory loops 1. Pulmonarycirculation Pulmonaryarteries transport blood away from the right ventricle to the lungs for the exchange of oxygen and carbon dioxide and return oxygenated blood to the heart, left atrium, via the pulmonary veins.

2. Systemic circulation Transports blood from the left ventricle through the aorta to all parts ofthe body and returns it to the right atrium through the superior and inferior venae cavae and the cardiac veins.

B. Heart Is a hollow, muscular, four-chambered organ that pumps blood to the two separate circulatory loops mentioned previously, the pulmonary circulation and the systemic circulation. Is regulated in its pumping rate and strength by the ANS, which controls the nonnal pacemaker, the sinoatrial node. • Receives oxygenated blood from the right and left coronary arteries off the ascending aorta.

C. Blood vessels Carry blood to the lungs, where carbon dioxide is exchanged for oxygen. Carry blood to the Intestines, where nutritive materials In fluid form are absorbed, and to the endocrine glands, where hormones pass through the vessel walls and are distributed to target cells. • Transport waste products from tissue ftuids to the kidneys, intestines, lungs, and skin, where •

they are excreted. Axe of four types: arteries, veins, capillaries, and sinusoids.

1. Artariaa • •

•

Carryblood away from the heart to the capillary beds and have thicker walls than do therr correaponding veins. Consist of three main types: the large elastic arteries; the distrlbutive, named, muscular arteries; and the smallest are arterioles found before a capillary bed. The precaplllary arterioles are vital to the maintenance of blood pressure.

12

BRS Graa Allatamy

2. Capillaries • Are composed of endothelium and its basement membrane and connect the arteriolea tovenules. • Are the sites fur Ille exchange of carbon dimdde, oxygen, nutrients, and waste products between the tissues and the blood. • Are absent in the comea, epidermis, and hyaline cartilage and may be absent in some areas where the arterioles and venules have direct connections (artariDY11nou1 anastomOHS or shunll), which may occur in the skin of the nose, lips, fingers, and ears, where they conserve body heat.

CLINICAL CORRELATES

Aneurysm is a circumscribed dilatation of an artery or the heart as a result of breakdown of the wall and is caused by an atherosclerosis (accumulation of fat, cholesterol, and calcium that forms plaque in the arterial wall), changes in the formation of tissue layers within the arterial wall, or high blood pressure, giving a greater risk of rupture. Atheroacl1ro1i1 is a pathology of arteries caused by narrowing of the artery because of the deposition of fat, cholesterol, and calcium {atheroma) in the a rte rial walls. Narrowing end blockage of arteries in the brain cause ischemic stroke, and narrowed and blocked coronary arteries lead to hean attacks. Typically, myocardial infarctions occur when a clot blocks a narrowed artery. Arteriosclarosis is a thickening and hardening of the arteria I walls with resulting loss of elasticity. It may be caused by fibrosis and calcification of the arteria I walls (the site of an atharoma) and develops with aging, high blood pressure, diabetes, and other conditions. Varicose vain1 are enlarged and tortuous veins that develop mast commonly in tile superficial veins of the lower limb because of reduced elasticity and incompetent valves in the veins orthrombophlebitis of the deep veins. 3. Veins • Return blood to the heart from the capillary beds and consist ofthe pulmonary veins, which retum mygenated blood to the left atrium ofthe heart from the lungs, and the systemic veins, which renim deoxygenated blood to the right atrium of the heart from the rest ofthe body. • Pulmonaryveins feed the systemic outflow, and the systemic venous returnis needed to

produce pulmonary blood ftow. Contain valves that prevent the reflux of blood, and each muscular artery may have two veins (YIDll comitantas) that closely accompany it into the limbs. 4. Sinusoids • Are wider and more irregular than capillaries and substitute for capillaries in some organs, such as the liver, spleen, red bone marrow, adenohypophysis, suprarenal cortex, and parathyroid glands. • Often contain phagocytic cells on their walls and form a part of the reticuloendolhelial system, which is concerned chietly with phagocytosis and antibody formation. 5. Portal system • Is a system ofvessels in which blood collected from one capillary network passes through a large vessel(s) and then a second capillarynetwork before it returns to systemic circulation. • Consists of the hepatic portal system in which blood from the intestinal capillary bed passes through the hepatic portal vein and then hepatic capillariea (sinusoids) to the hepatic veins, and the hypophyseal portal system in which blood from the hypothalamic capillaries passes through the hypophyseal portal veins and then the pituitary capillary sinusoids to the hypophyseal veins. •

II. LYMPHATIC SYSTEM • Provides an important immune mechanism for 1he body. • Provides a route for transporting fat and large protein molecules absorbed from the intestine to the thoracic duct.

l3JIEtlij Introduction

13

A. Lymphatic vn11ls • Serve as one-way drainage toward the heart and return lymph to the bloodstream through the thoracic duct (the largest lymphatic vessel) or the right lymphatic duct. • Function to absorb large protein molecules and transport them to the bloodstream because the molecules cannot pass through the walls of the blood capillaries back into the blood. Carry lymphocytes from lymphatic tissues to the bloodstream. • Have valves, which are constricted at the sites of valves; thus, vessels show a beaded appearance. Are absent in the brain, spinal cord, eyebells, bone marrow, splenic pulp, hyaline cartilage, nails, and hair. • Are not usually visible 1n dissections but are the major mute by which cancer metastasizes.

B. Lymphatic capillaries • Begin bllndly in most tissues. collect tissue fluid, and join to form large collecting vessels that pass to regional lymph nodes. Absorb lymph from tissue spaces and transport it back to the venous system. • Are called lactaals in the villi of the small intestine, where they absorb emulsified fat

C. Lymph nodes • Are organized collections of lymphatic tissue permeated by lymph channels. Contain lymphocytes and plasma cells and filter the lymph. Nonnally, not easily palpated. But can be palpable, hard, and painless with a metastasis or enlarged and tender when associated with infections. Trap bacteria and metastatic cells drained from an infected area or tumor and contain retlculoendothellal cells and macrophages (phagocytic cells) that ingest and digest non-self-epltopes for presentation to lymphocytes.

D. Lymph • Is a clear, straw-colored 8uid that is collected from the intercellular spaces. • Typically is acellular until lymphocytes are added in its passage through the lymph nodes. Its constituents are similar to blood plasma (e.g., proteins, fats, and lymphocytes). • Often contains digested fat droplets (called chyla) that come from intestines. • Is filtered bypassing through several lymph nodes before entering the venous system.

ORGAN SYSTEMS I. DIGESTIVE SYSTEM Consists of three divisions of the visceral tube, the mouth, the pharynx. and the alimentllry canal, comprising the esophagus, the stomach, the small intestine, and the large intestine. • Also contains accessory organs and glands to aid in digestion and nutrient storage, Including the salivary glands, liver, gall bladder, and pancreas. • Performs specific functions: essential food-processing activities. In the mouth, the food Is moistened by saliva; Is masticated and mixed by the mandible, teeth, and tongue; and Is propelled by the pharynx and esophagus Into the stomach, where It ls mixed with the gastric juice and converted Into chyme. • Performs specific functions: in the small intntine, the food or chyme is digested by secretions from glands in the intestinal wall and from the livei; gallbladder, and pancreas; and digested end products are allaarbed into the blood and lymph capillaries in the intestinal wall. Performs specific functions: in the large intestine, water and 1l1ctrolyte1 are absorbed, and the waste products are transported to the rectum and anal canal, where they are eliminated as feces. liver stores and releases glucose, breaks down toxins, and marshals cholesterol metaboliBm.

14

BRS Graa Allatamy

II. RESPIRATORY SYSTEM • Consists of a conducting ponion lhat tnn1ports filtered, humidified, and warmed air to the lungs. Includes the nose/nasal cavity and paranasal sinuses, pharynx, 1.arym, trachea, and bronchi. • Consists of a respiratory portion in the lungs, which contain the terminal air sacs, or alvaoli, where gas exchange occurs; oxygen in the air is exchanged for carbon dioxide in the blood. • Air movements at rest are aided by the diaphragm and thoracic cage. • Is concerned with speech, which involves the intermittent release of exhaled air and the opening and closing of the glottis.

Ill. URINARY SYSTEM • Kid nays produce urine and are important in maintaining water and electrolyte balance, acid-base balance, regulating urine volume and composition, regulating blood volume, and in eliminating waste products from the blood. Also, through structures in the kidney, stimulates red blood cell production and helps in the control of blood pressure. • Ureters carry urine from the kidney to the urinary bladder. • Bladder stores urine and drains through the urethra out of the body.

IV. REPRODUCTIVE SYSTEM A. Male raproducliva system • Includes tastes that produce 1p1nnato.zoa and androgenic honnones. • Hu ducts (epididymis, ductus deferens, and ejaculatory ducts) that transmit spermatozoa from the testis to the prostatic urethra. • Glands, such as the seminal vesicles, prostate gland, and bulbourethral glands, conttibute secretions to the seminal D.uid as it passes through the urethra. • The urethra passes the ejaculate to an opening at the tip of the external genital organ, the penis.

B. Female reproductive system • Consists of ovaries, uterine tubes, uterus, vagina, and external genital organs. The ovaries produce steroid honnones and also oocyt11 (ova or eggs) that are conveyed from the ovaries through the uterine tubes to the cavity of the uterus. Each ovulated oocyte is released into the peritoneal cavity of the pelvis; one of the uterine tubes captures the oocyte, where it begins its journey toward the uterus. The uterine tubas transmit spennatozoa in the opposite direction, and lenilizatian of an oocyte usually occurs within the expanded ampulla of a uterine tube. A fertilized oocyte becomes embedded in the wall of the uterus, where It develops and grows into a fetus, which passes through the uterus and vagina (together called the birth canal}. The vagina provides a passage for delivery ofan infant; it also receives the penis and semen during sexual intercourse. • Includes female external genitalia: the mons pubis, which is a fatty eminence anterior to the symphysls pubis; the labia majora, which are two large folds of the skin; the labia minora, which are two smaller skin folds that commence at the glans clitoris, lack hair, and contain no fat; the vestibule, which is an entrance of the vagina between the two labia minora; has the hymen at the vaginal orifice; and the clitoris (crura, body, and glans or head), which is composed largely oferectile tissue and is hooded by the prepuce of the clitoris.

l3JIEtlij Introduction

15

V. ENDOCRINE SYSTEM Ductless endocrine glands secrete honnones, or messenger molecules, directly into the blood circulation and are carried to body cells. Controls and inlllgratas the functions of other organ systems and plays a very Important role in reproduction, growth, and metabolism. Functions tend to be slower proce88e8 compared to those controlled by the nervous system. Pure endocrine organs include the pituitary, pineal, thyroid, parathyroid, and suprarenal glands. Other endocrine cells are contained in the pancreas, thymus, gonads, hypothalamus, kidneys, liver, stomach, and the walls of the intestine. Tropic honnon11 are hormones that regulate the functions ofother endocrine glands.

VI. INTEGUMENTARY SYSTEM Includes skin (integument) and its appendages, including sweat glands, sebaceous glands, hair, and nails. • Contains 11n1ory receptors associated with nerve endings for pain, temperature, touch, and pressure. • Represents the largest single organ in the body.

A. Skin Consists of the avascular epidermis as the superflclal, or surfacing, layer of stratified squamous epithelium that develops from ectoderm and has a keratinized layer on the outslde ofthe body; it ls thickest on the palms and the soles. The dennis is a deeper layer of connective tissue that develops largely from the mesoderm and contains downgrowtbs from the epldermis, such as hair follicles and glands. The hypodennis (subcutaneous tissue) is a fatty layer that lies deep to the dermis and is part of the superficial fascia. This layer is highly vascular and can serve as a route to administer medications via injection. • The skin is a protective layer. an extensive sensory organ and is sjgnificant in body temperature regulation, iluid balance, production of vitamin D, and at least some absorption.

B. Appendages of Iha skin Swait glands develop as epidermal downgrowths, have excretory functions, and regulate body temperature and fluid balance. • Sebaceous glands develop from the epldennis (as downgrowth.s from hair follicles into the dermis) that empties their oily sebum into hair follicles to provide a lubricant to the hair and skin and protect the skin from drying. • Hairs develop as epidermal downgrowths and function in protection, regulation of body temperature, and facilitate evaporation of perspiration. • Nails develop as epidermal thickenings to protect the sensitive tips of the digits and function in delicate manipulations.

HIGH-YIEW TOPICS Appendicular skeleton includes the upper and lower limbs and the pectoral and pelvic girdles. • Axial skeleton includes the skull, vertebral column, ribs, and sternum. • Bonn serve as a reservoir far calcium and pho1phoru1 and act as biomecbanical levers on which muscles act to produce the movements.

16

BRS Gross Anatomy Long bones have a shaft (diaphysis) and two ends (epiphyses). The metaphysis is a part of the diaphysis and is the growth zone between the diaphysis and epiphysis during bone development. Sesamoid bones develop in certain tendons and muscles and reduce friction as well as increase ability to transmit muscular force.

Osteoblasts synthesize new bone and osteoclasls function in the resorption and remodeling ofbone. Osteomalacia is a gradual softening of the bone caused by failure of the bone to calcify. Ostaopenia is a decreased calcification of bone or a reduced bone mass. Osteoporosis is an age-related disorder characterized by decreased bone mass and increased susceptibility to factures. It occurs when bone resorption outpaces bone formation (osteoclastic activity is greater than osteoblastic activity). Osteopetrosis is an abnormally dense bone, obliterating the marrow cavity, because of defective resorption of immature bone (osteoblastic activity is greater than osteoclastic activity). The nerve supplying a joint also supplies the muscles that move the joint and the skin covering the insertion of such muscles (Hilton law). Osteoarthritis is a noninflammatory degenerative joint disease characterized by degeneration of the articular cartilage and osseous outgrowth at the margins. Rheumatoid arthritis is an inflammatory disease of the joints. It is an autoimmune disease in which the immune system attacks the synovial membranes and articular structures, leading to deformities and disability. Gout is a painful form of arthritis and is caused by too much uric acid in the blood. Uric acid crystals are deposited in and around the joints, causing inflammation and pain, stiffness, and swelling of the joint tissues. Lou Gehrig disease (amy01rophic lateral sclarosis/ALS) is a fatal neurologic disease that attacks the neurons responsible for controlling voluntary muscles. The muscles gradually weaken and atrophy; the brain is unable to control voluntary movement ofthe body; and patients lose the ability to breath, swallow, and speak. Nervous system is divided into the central nervous system (CNS), consisting of the brain and spinal cord, and the peripheral nervous system (PNS), consisting of 12 pairs of cranial nerves and 31 pairs of spinal nerves and their associated ganglia. It is divided functionally into the somatic and visceral (autonomic) nervous system. Ganglion is a collection of neuron cell bodies outside the CNS, and a nucleus is a collection of

neuron cell bodies within the CNS. Neurons in cranial or spinal ganglia are unipolar (pseudounipolar) types. Axons carry impulses away from the call body, whereas the dendrites carry impulses toward Iha cell body. Myelin is the fatlike substance forming a sheath around certain nerve fibers and is formed by Schwinn cells in the PNS and oligodendrocytes in the CNS. The autonomic nervous system (ANS) is responsible for the motor innervation of smooth muscle, cardiac muscle, and glands and is divided into the sympathetic, parasympathetic, and enteric divisions. Preganglionic neuron cell bodies are in the CNS, and postganglionic neuron cell bodies are in ganglia in the PNS. ANS consists of chol inargic fibers (sympathetic preganglionic, parasympathetic preganglionic, and parasympathetic postganglionic) and adrenergic fibers {sympathetic postganglionic) except those to sweat glands (cholinergic). Sympathetic nervous system functions in emergencies or catabolism (energy consumption), preparing for fight or flight, whereas the parasympathetic nerves function in homeostasis or anabolism {energy conservation), tending to promote quiet and orderly processes of the body. Cerebrospinal fluid (CSF) is produced byvascular choroid plexuses in the brain ventricles and found in the subarachnoid space. Multiple sclerosis (MS) is a nervous system disease that causes destruction of myelin in the CNS {spinal cord and brain), leading to sensory disorders and muscle weakness. Symptoms also include numbness, visual and cognitive impairments, loss of coordination and balance, slurred speech, bladder incontinence, fatigue, and depression. Coronary arteries arise from the ascending aorta and supply blood to the heart. Portal venous system consists of the hepatic portal system in which blood from the intestinal capillary bed passes through the hepatic portal vein and then hepatic capillaries {sinusoids) to the hepatic veins, and the hypophyseal portal system in which blood from the hypothalamic

l!1ltmJll

Introduction

17

capillaries passes through the hypophyseal portal veins and then the pituitary capillary sinusoids to the hypophyseal veins. Varicose veins are dilated veins that develop in the superficial veins of the lower limb because of reduced elasticity and incompetent valves in the veins or thrombophlebitis of the deep veins. Aneurysm is a circumscribed dilation ofthe wall of an artery or the heart and caused by a weakness of the arterial wall, an atherosclerosis (accumulation offat, cholesterol, and calcium which form plaque in the arterial wall), or high blood pressure, giving a greater risk of rupture. Atherosclerosis is a narrowing of the artery because of fatty plaque formation in the arterial wall. Narrowing and blockage of arteries in the brain cause stroke, and narrowed and blocked coronary arteries lead to heart attacks. Arteriosclerosis is a thickening and hardening of the arterial wall. Lymphatic system provides an important immune mechanism including clearing infections from the bloodstream, provides a route for transporting fat and large protein molecules, and is involved in the metastasis of cancer cells. Thoracic duct begins in the abdomen at the cistema chili; drains the lower limbs, pelvis, abdomen, left thorax, left upper limb, and left side of the head and neck; and empties into the junction of the left internal jugular and subclavian veins. Right lymphatic duct drains the right sides of the thorax, upper limb, head, and neck and empties into the junction of the right internal jugular and subclavian veins. Lymph nodes are organized collections oflymphatic tissue and are an important part ofthe immune system. Lymph nodes are the main source of lymphocytes of the peripheral blood, play a role in antibody production, and as part of the reticuloendothelial system, serve as a defense mechanism by removing noxious agents, such as bacteria and toxins.

Review Test

Directions: Bach of the numbered items or incomplete statements in this section is followed by answers or by completions of the statement Select the one-lettered answer or completion that is belt in each case.

1. A 22-year-old man presented to his family physician with a laceration of the fibrous sheets or bands that cover his body Wlder the skin and surround the muscles. Which of the following structures would most likely be injured? (A) Tendon (B) Fascia (C) Synovial tendon sheath (D) Aponeurosis (E) Ligament

l. After examination by her neurologist a patient is told that her parasympathetic nerves are damaged. Which of the following muscles would most likely be affected? (A) Muscles in the hair follicles (B) Muscles in blood vessels (C) Muscles that act at the elbow joint (D) Muscles in the gastrointestinal. (GI) tract (E) Muscles enclosed by eplmysium

3. A 46-year-oldmale patient with high blood pressure was seen in the emergency department and found to have leakage of blood from the blood vessel that normally carries richly oxygenated blood. Which of the following vessels would most likely be damaged? (A) Superiorvenacava (8) Pulmonary arteries (C) Pulmonaryveins (D) Portal vein (E) Coronary sinus

4. A 26-year-old man was stabbed in a bar fight Axons of the general somatic efferent {GSB) neurons to the shoulder muscles were severed. The damaged amns: (A) Would carry impulses toward the cell bodies

(B) Would carry impulses away from the cell bodies

18

(C) Would carry pain Impulses (D) Are several in numbers for multipolar neurons (E) Are found primarily in the gray matter

5. A 76-year-old homicide victim suffered a laceration of the posterior intercostal nerves by a penetrating knife wound. Under microscopy, the pathologist observed numerous degenerated cell bodies of the unipolar or pseudounipolar neurons. Which of the following structures would most likely provide the abnormal cell morphology? (A) Ventral horn of the spinal cord (B) Lateral hom of the spinal cord (C) Dorsal horn of the spinal cord (D) Dorsal root ganglion (E) Sympathetic chain ganglion &. A 59-year-old anatomy professor came to her doctor's omce for a neurologic examination.. Her physician told her that synapses are normally absent In or on which of the following structures? (A) Anterior horn of the spinal cord (B) Dorsal root ganglia (C) Sympathetic chain ganglia (D) Dendrites (E) Cell bodies

1. A 27-year-old woman involved in a car accident is brought into the emergency department Her magnetic reaonance imaging reveals that she has laceration of the spinal cord at the IA spinal cord level. Which of the following structures would you expect to be intact? (A) Dorsal horn (B) Lateralhom (C) Ventral horn (D) Gray matter (E) White matter

l!1ltmJll 8. A 33-year-old man slept on his bed in a funny position and now complains of feeling severe pain when he tries to turn his neck. The physician realizes that the problem is in his pivot (trochoid) joint Which of the following joints would most likely be examined? (A) Atlanta-occipital joint (B) Atlantoaxial joint (C) Carpometacarpal joint (D) Proximal tibiofibular joint (E) Intervertebral disks

9. A patient presents with a loss of sensation to the skin overlying the shoulder. Injury to which of the following nerve cells would most likely affect the conduction of sensory information to the central nervous system?

(A) Multi.polar neurons (B) Bipolar neurons (C) Unipolar or pseudounipolar neurons (D) Neurons in the ventral ham (E) Neurons in sympathetic chain ganglia

10. A 7-year-old girl comes to the emergency department with severe diarrhea. Tests show that the diarrhea is due to decreased capacity of normal absorption in one of her organs. Which of the following organs is involved?

(A) Stomach (B) Gallbladder (C) Large intestine (D) Liver (E) Pancreas

11. A 16-year-old girlcomes to a local hospital with urinary urgency and frequency. Her urologist's examination and laboratory test results reveal that she has difficulty in removing wastes from the blood and in producing urine. Which of the following organs may have abnormal functions?

(A) Ureter (B) Spleen (C) Urethra (D) Bladder (E) Kidney

12. A 53-year-old man with a known history of emphysema is evaluated in the emergency department. Laboratory findings and physical examination indicate that the patient is unable to exchange oxygen in the air and carbon dioxide

Introduction

19

in the blood. This exchange occurs in which portion of the respiratory system?

(A) Bronchi (B) Alveolar (air) sac (C) Nasal cavity (D) Larynx (El Trachea

13. A 26-year-old woman has an amenorrhea, followed by uterine bleeding, pelvic pain, and pelvic mass. Her obstetrician performed a thorough examination, and the patient was diagnosed as having an ectopic pregnancy. Which of the following organs is most likely to provide a normal site offertilization?

(A) Fundus of the uterus (B) Ampulla of the uterine tube (C) Fimbriae (D) Infundibulum of the uterine tube (El Body of the uterus

14. A 29-year-old woman with abdominal pain was admitted to a local hospital, and examination shows that a retroperitoneal infection is affecting a purely endocrine gland. Which of the following structures is infected?

(A) Ovary (B) Suprarenal gland (C) Pancreas (D) Liver (El Stomach

15. A 36-year-old man suffers a first-degree burn on his neck, arm, and forearm from a house fire. Which of the following skin structures or functions is most likely damaged or impaired?

(A) GSE nerves (B) Parasympathetic general visceral efferent nerves (C) Trophic hormone production (D) Exocrine gland secretion (El Vitamin A production

16. A 19-year-old man is diagnosed with multiple sclerosis (MS). Which of the following nervous structures would most likely be affected by this disease?

(A) Trigeminal ganglion (B) Superior cervical ganglion (C) Optic nerve (D) Facial nerve (El Spinal accessory nerve

Answers and Explanations

1. The answer is B. (Muscular System: Il.H) The fascia is a fibrous sheet or band that covers the

2.

3.

4.

5.

&.

7.

8.

9.

10.

20

body under the skin and invests the muscles. Although fasclae are fibrous, tendons connect muscles to bones or cartilage, aponeUJOses serve as the means of origin or insertion of a fiat muscle, and ligaments connect bones to bones or cartilage. Synovial tendon sheaths are tubular sacs filled with synovial fluid that wrap around the tendons. The answer is D. (Muscular System: 1.C} Smooth muscles in the GI tract are innervated by both parasympathetic and sympathetic nerves. Smooth muscles in the wall of the blood vessels and arrector pili muscles in hair follicles are innervated only by sympathetic nerves. Muscles that act at the elbow joint and muscles enclosed by epimysium are skeletal muscles that are innervated by somatic motor (general somatic efferent (GSB]) nerves. The answer ii C. (Circulatory System: I.A.I) Pulmonary veins renun oxygenated blood to the heart from the lungs. Pulmonary arteries carry de oxygenated blood from the heart to the lungs for oxygen renewal. The portal vein carries deoxygenated blood with nutrients from the intestine to the liver. The superior vena cava and coronary sinus carry deox:ygenated blood to the right atrium. The answer is B. (Nervous System: I) The axons of the neurons carry impulses away from the cell bodies, and dendrites carry impulses to the cell bodies. The axons contain sensory or motor fibers. Multipolar neurons have several dendrites and one axon. The GSE neurons do not carry sensory Impulses. The gray matter of the central nervous system consists largely of neuron cell bodies, dendrites, and newoglia, whereas the white matter consists largely of axons and neuroglia. The answer is D. (Nervous System: II.B.3) Ventral, lateral, and dorsal horns and sympathetic chain ganglia contain multipolar neurons, whereas the dorsal root ganglion contains unipolar or pseudounlpolar newon.s. Alaceration of the intercostal nerve injures GSB, postgangllonic sympathetic general visceral efferent (GVB), general visceral. afferent (GVA), and general somatic afferent (GSA) fibers, whose cell bodies are located in the anterior hom, sympathetic chain ganglia, and dorsal root ganglia. The answer is B. (Nervous System: I\T.B) Dorsal root ganglia consist of cell bodiea of the unipolar or pseudounlpolar neurons and have no synapses. A:xosomatlc and amdendrltic synapses are the most common, but uouonic and dendrodendrltic contactB are also found in many nerve tissues. The answer is B. (Nervous System: I\T.B) The lateral horns are found In the gray matter of the spinal cord be~ Tl and L2 and also between S2 and S4. Therefore, the lateralhoms are absent at the IA spinal cord level The answer is B. (Skeletal. System: D.C.3) The atlantoaxlal joint is the plvot or ttochold folnt. The atlanto-occlpital joints are the condyloid (ellipsoidal) joints; the carpometacarpal joint of the thumb ls the saddle (sellar) Joint; and the proximal tibioflbular joint is the plane (gliding) joint The intervertebral. disk is the secondary cartilaginous (symphysis) joint The answer is C. (Nervous System: I\T.C.1) Sensation from the skin ls carried by GSA fibers, and their cells are unipolar or pseudounlpolar types located in the dorsal root ganglia. Multipolar neurons and neurons in the ventral horn and in sympathetic chain ganglia are motor neurons. Bipolar neurons are sensory neurons, but they are not somatic sensory neurons. The answer is C. (Organ Systems: The large intestine absorbs wate11 salts, and electrolytes. Hence, the patient's diarrhea stems from malabsorption. The stomach mixes food with mucus and gastric juice, which contains hydrochloric acid and enzymes, and fonns chyme. The gallbladder receives bile, concentrates it, and stores it The liver produces bile, whereas the

n

l!1ltmJll

Introduction

21

pancreas secretes pancreatic juice, which contains digestive enzymes and releases hormones, such as insulin and glucagon.

11. The answer is E. (Organ Systems: III) The urinary system includes the kidneys, which remove wastes from the blood and produce the urine; the ureters, which carry urine; the urinary bladder, which stores urine; and the urethra, which conveys urine from the bladder to the exterior of the body. The spleen filters blood to remove particulate matter and cellular residue, stores red blood cells, and produces lymphocytes. Because the patient is not producing urine properly, the malfunctioning organs are the kidneys.

12. The answer is B. (Organ Systems: II) The respiratory portion of the lung contains the alveolar (air) sacs or alveoli, which are surrounded by networks of pulmonary capillaries. Oxygen and carbon dioxide exchange occurs across the thin walls of the alveoli and blood capillaries with the aid of the diaphragm and thoracic cage. The nasal cavity, larynx, trachea, and bronchi are air-conducting portions.

13. The answer is B. (Organ Systems: IY.B) Fertilization occurs in the ampulla of the uterine tube, and a fertilized oocyte forms a blastocyst by day 7 after fertilization and becomes embedded or implanted in the wall of the uterus during the progestational (secretory) phase of the menstrual cycle. Fertilization is the process beginning with the penetration of the secondary oocyte by the sperm and completed by fusion of the male and female pronuclei.

14. The answer is B. (Organ Systems: V) The suprarenal gland is a retroperitoneal organ and is a purely endocrine gland. The pancreas is a retroperitoneal organ and contains endocrine cells, but it is not a purely endocrine gland. The liver and stomach contain endocrine cells, but they are not purely endocrine glands and also are surrounded by peritoneum. The ovary contains endocrine cells and is located in the pelvic cavity.

15. The answer is D. (Organ Systems: VI) Skin has sweat glands and sebaceous glands, which are exocrine glands. Skin produces vitamin D, but it does not produce a trophic hormone and vitamin A. In addition, skin contains no GSE and parasympathetic GVE nerve fibers.

16. The answer is C. (Nervous System: III Clinical Correlates) Multiple sclerosis affects only axons in the CNS (spinal cord and brain) that have myelin sheaths formed by oligodendrocytes. The optic nerve is considered to be part of the CNS because it is derived from an outpouching of the diencephalon. All other nervous structures are in the PNS and have their myelin sheaths formed by Schwan cells.

Back

VERTEBRAL COLUMN I. GENERAL CHARACTERISTICS (Figures 2.1 to 2.3) The vertebral column typically consists of 33 vertebrae (7 cervical, 12 tho acic, 5 lumbar, 5 fused sacral, and 4 fused coccygeal vertebrae). The bony vertebral column crea es an axial strut for the support of the body, protects the spinal cord, provides a pedestal for ~eJiead, nd allows movement of the rib cage for respiration by articulating with the ribs. ~ The normal forward curvature (kyphosis) in the thoracic and sacral regions corresponds to the primary curvatures seen in the embryo, whereas with upright:ROS ure after birth and during infancy, the cervical and lumbar vertebrae develop gentle backward curves (lordosis) called secondary curvatures.

Angle of mandible

Air in trachea

Transverse process of first thoracic vertebra

First rib

Spinous process of seventh cervical vertebra

Tubercle of first rib

Clavicle

Articular facet Head of first rib

FIGURE 2.1. Anteroposterior radiogra ph of the cervical and upper thoracic vertebrae.

22

l3lJ1EIUI Back

23

-Body of vertebra

Conus madullarls -

lntervertebral disk Cerebrospinal

tluld Cauda equina _..

Sacral promontory-

A

B

RGURE2.2. Sagittal magnetic resonance imaging (MRI) scans of the vertebral column. A: Midsagittal view. B: Parasagittalview.

Posterior tubercle

Tl'anS;l.,.. Medulla--"~-"'------~

37

Occipital lobe Cerebellum Pia mater II"'.&4--Ara,chnold mater ~----oura mater n+---+--Subarachnoid space i+---+--Subdural apace

+--___,1--Dura mater

Subarachnold space Filum tenninale

ubdural space

Filum of dura mater

RGURE2.1D. Meninges.

II. SPINAL NERVES • Consist of31 pairs of nerves (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal). • Are formed within an intervertebral foramen by wrion of the ventral and dorsal roots. The dorsal mot has a ganglion that contains pseudowrlpolar cell bodies ofsensory neurons. • The dorsal primary rami innervate the skin and deep muscles of the back. • The venb'al primary rami form the cervical plexus (CI-C4), brachiaI plexus (CS-Tl) for the upper limb, intarcostal narvas (Tl-Tll), the subcastal nerve (TI2), the lumbar pluus (LI-IA), and the lumbosacral plexus (IA-S4} for the lower limb and perineum. • Are connected with the sympathetic chain ganglia by rami cammunicantas.

38

BRS Graa Allatamy

• Are mixed nerves, containing general functional components (ie., somatic afferent [SA], somatic efferent [SB], visceral afferent [VA], and visceral efferent (VE]). • Sensory fibers in spinal nerves (SA and VA) fibers have cell bodies in the dorsal root ganglion at all

spinal levels. Somatic motor ISE) fibers come from multipolar neurons located in the anterior horn ofthe spinal cord. • Praganglionic sympathetic IVE)fibars have cell bodies located in the lateral horn of the spinal cord (segments Tl through L2). • Preganglionic parasympathetic (VE) fibers have cell bodies in the lateral horn of the spinal cord segments S2 through S4. These autonomic fibers leave the sacral spinal nerves via the pelvic splanchnic nerves.

CLINICAL CORRELATES

Chicken pox lvaricellal is caused by a primary infection of the varicalla zosttr virus, which later resides latent in the cranial (i.e., trigeminal) or dorsal root ganglia. Typically marked by generalized vesicular eruption of the skin and mucous membranes. Highly contagious, end a patient may have a runny or stuffy nose, sneezing, cough, itchy rash, fever, and even abdominal pain. Shinglas (harpas zollarl is a reactivation (secondary infection} of chicken pox virus, varicella zostar virus, that remains latent in the dorsal root ganglia of spinal nerves and the sensory ganglia of cranial nerves. The cutaneous manifestation from activation of the virus in the dermatome corresponds to the activated ganglion down to the sensory nerve to produce severe neuralgic pain and an eruption of a vesicular rash. Believed to occur because of a reduction in immune status.

Ill. MENINGES (see Figures 2.2 and 2.10) A. Piamater • Is the innermost meningeal layer, which is closely applied to the spinal cord. It also envelops the blood vessels to the surface of the spinal cord. • Has lateral extensions called denticulate ligaments between the dorsal and the ventral roots of spinal nerves and an inferior extension known as the filum tenninale.

CLINICAL CORRELATES

Meningitis is inflammation of the meninges. Viral meningitis may be milder and occurs more often than bacterial meningitis. The treatments may include supportive therapies and antiviral medications. Bacterial meningitis {purulent meningitis) is a life-threatening illness and may result in brain damage or death, even if treated with required antibiotics. Meningitis is also caused by fungi, chemical irritation or drug allergies, and tumors. Its symptoms include fever, headache, stiff neck. brain swelling, shock, convulsions, nausea, and vomiting. B. Arachnoid matar • Is a transparent layer just under the dura connected to the pia mater by weblike trabeculations. • Between the arachnoid and the pia, the subarachnoid space is filled with cerebraspinal fluid (CSF). The enlarged subarachnoid space around the cauda equina from vertebral levels Ll to S2 is called the lumbar cisttrn.

C. Duramater • Is the tough. fibrous, outermost layer of the meninges. • The subdural space is a potential space between the arachnoid and the dura. It extends inferiorly to the second sacral vertebral level and contains only sufficient fluid to moisten the surfaces of two membranes.

• Theepidural space ls enemaI to itand contains the internal vertebral venous plexus and epidural fat.

EiD1ttfl Back

39

CUNICAL

Caudal (epidural) anastfluia is used to lllock the spinal narvH in the epidural space by injection of local anesthetic agents via the sacral hiatus located between 1he sacral cornua. It is used for surgery on the rectum, anus, genitals, or urinary tract and for culdoscopy. Obstetricians use this method of nerve block to relieve pain during labor and childbirth, and its advantage is that1he anesthetic does not affect the infant Spinal anastfl11i1 is introduction of anesthetic into the dural sac and blocks neural transmission to aII areas below the level of injection. Pudenda! anmhnia is the introduction of anesthetic into the pudenda! canal and provides pain relief in the perinea! region. Lumbar puncture (spinal tap) is the introduction of a needle into the subarachnoid space in the lumbar region (lumbar cistern), usually between the laminae of vertebrae L3 and L4 or vertebrae L4 and L5 during maximally flexing the vertebral column. It allows measurement of CSF pressure and withdrawal of a sample of the fluid for microbial or chemical analysis and also allows introduction of anesthesia, drugs, radiopaque material, and chemotherapy into the subarachnoid space.

CORRELATES

CUNICAL

Cauda equine syndrome is commonly caused by a lumbar disk that protrudes into the spinal canal and compresses against the narve roots of the lumbar spine (Figure 2.11 ). This may lead to numbness and tingling and later stages paralysis, loss of bowel or bladder function, and loss of saxua I function. Spinal cord compression occurs higher up in the spinaI column, and the presence of a tumor or mass or intravertebral disk compresses against1he spinal cord itself, thereby leading to loss of nervous system function at1hat level (Figure 2.12). Treatment may include surgery to remove the offending agent and take the pressure off 1he nerve roots and or spinal cord, steroids for tumor control, antibiotics for infections/abscesses in that confined space, and radiation for quick treatment of metastatic cancer.

CORRELATES

F1GURE2.11. Cauda equina syndrome.

BRS Graa Allatamy

RGUREZ.12. Spinal cord compression.

IV. STRUCTURES ASSOCIATED WITH THE SPINAL CORD A. Cauda equina (·Horse's Tail·) • Is a bundle of dorsal and ventral roots oflumbar and sacral spinal nerves that surround the

filum terminal•. • Is located within the subarachnoid space (lumbar cistern) below the level ofthe conus medullarls. • Is free to float in the CSP within the lumbar cistern and is therefore not damaged during a spinal tap.

B. Denticulate ligamants • Are lateral extensions of the spinal pia mater, consisting ofZ1 pail"I of toothpick-like processes. • Extend laterally from the pia through the arachnoid to the dura mater between the dorsal and the ventral roots ofthe spinal nerves. • Help stabilize the spinal card within the subarachnoid space.

C. Alum tenninala (intemum) • Is a prolongation of the pia mater from the tip (conus medullaris) ofthe spinal cord at the level of12. • Uea in the midst of the cauda equina and ends at the S2 vertebral level by attaching to the apex of the dwal sac. • Blends with the dura at the apex of the dural sac, and then the dura continues downward as the filum terminal• extemum, which is attached to the dorsum of the coccyx.

D. Carabraspinal fluid • Is contained in the subarachnoid space ofboth the brain and the spinal cord between the arachnoid and pia mater. • Is formed by vascular choroid pluu111 ln the ventricles of the brain. • Circulates through the ventricles, enters the subaracb.noid space, and eventually filters into the venous system through arachnoid villi, projectinginto the dural venous sinuses, particularly the superior saglttal sinus.

l3lJ1EIUI Back

41

V. DERMATOME. MYOTOME. AND SCLEAOTOME A. D1nn11om1 (Figure2.13) • Is an area of skin innervated by sensory fibers derived from a single spinal nerve segment. Knowledge of the dermatome map is useful clinically to localize lesions to a nerve root or spinal cord level.

B. Myotome • Is a group of muscles innervated by motor fibers derived from a single spinal nerve segment. Myotomes are formed from embryonic somites.

C. Sclerotome • Is the area of a bone innervated from a single spinal segment Sclerotomes also develop from somites.

LS

RGURE2.13. Schematic demarcation of darmatomes shown as distinctsegmants.

C2

BRS Graa Allatamy

VI. DEVELOPMENT OF BACK STRUCTURES A. Development of vertebral column • The embryonic mesoderm dilierentiates htto the paraDal mesoderm., httermediate mesoderm., and lateral plate mesodenn. • The parui.al mesoderm. divides into 1omitn, and each somite differentiates into the 1cl1rotam1 (a ventromedlal part) and the d1nnatomyatDm1 (a dorsolateral part), which further differentiates into the myotome and the damatoma. • Mesencbymalcells from the sclerotome farm condensations around the neural tube and the notochord. • The caudal half of one sclerotome fuses with the cranial half of the next sclerotome to form a

vertebral body. • The notochord degenerates ht the vertebral body, but its remnant forms the nucleus p11lpo1111 In the lntervertebral disks. • The annulus fibro1111 of the intervertebraldisk is derived from mesenchymal cells ofsclerotome situated between adjacent vertebral bodies.

B. Development of spinal cord and meninges (see Figure 2.10) 1. Neural tube farmatiDn (neurulatian) • The notochonl induces the overlying ectodenn to differentiate into neuroectoderm to form the neural plate. • The neural plata (neuroectoderm) folds to form the neural tube. As the neural plate folds, some cells differentiate into neural crest cells. • The neural tuba htitially remahts open at cranial and caudal neuropores. The brain develops from cranial swellings of the neural tube after closure ofthe cranialneuropore. The spinal cord develops from the caudal neural tube on closure of the caudal neuropore. • Neuroblasts form all neurons with.ht the brain and sphtal cord, Including preganglionic sym· pathetic and parasympathetic neurons. Z. Neural crest calls • Develop from the junction of the neural tube and surface ectoderm. • Give rise to dorsal mot ganglia, autonomic ganglia, and adrenal medulla. In addition, neural crest cells give rise to melanocytes, cranlofacial bones and cartilage, and parts ofthe developing heart

1 Meninges • The dura mater arises from the mesoderm that surrounds the neural tube. Recent research suggests that neural crest cells may also contribute to dural development. • The pia mater and the arachnoid membrane arise from neural crest cells. C. Development of back muscles • Differentiating somites give rise to segmental myotomes, and each myotome splits into a dorsal apimere (dorsal part of a myotome) and a ventral hypomera (ventrolateral part ofa myotome). • The epimere gives rise to deep back {epaxial) muscles that are innervated by dorsal primary rami ofspinal nerves. • The hypomere gives rise to bodywall (hypaxial) muscles that are innervated byventral primaryrami ofspinal nerves. The prevertebral and postvertebralmuscles develop from the segmental myotmnes. • Umb muscles arise from the hypomere, migrate into limb buds, and are innervated by ventral primary rami of spinal nerves. • Superficial back muscles are muscles of the upper limb and thus develop from the hypomere and are innervated by ventral primary rami ofsphtal nerves.

HIGH-YIELD TOPICS • Vertebral column consists of 33 vertebrae, including the 7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral, and 4 fused coccygeal.

• Atlas is the Cl vertebra, supports the skull, and helps make nodding movements possible. The axis has a dens that helps the head to rotate.

l!iJtt:ltJij Back

43

Alar ligament prevents excessive rotation of the head. The ligamentum nuchae is the extension of the supraspinous ligament in the cervical region. The ligamentum flavum connects adjacent laminae. lnterverlebral disks consist of a central nucleus pulposus with a surrounding annulus fibrosus and serve as shock absorbers. The nucleus pulposus is a remnant of the embryonic notochord and may herniate through a ruptured annulus fibrosus, thereby impinging on the roots of the spinal nerve. Most herniated disks occur at U to LS. Primary curvatures are located in the thoracic and sacral regions and develop during embryonic and fetal periods, whereas the secondary curvatures are located in the cervical and lumbar regions. Spina bifida is a defective closure ofthe vertebral arch associated with maternal folic acid deficiency and includes {a) spina bifida occulla-a failure of the vertebral arch to fuse (bony defect only with a small tuft of hair over the affected area of skin), (b) meningocela-a protrusion of the meninges through theunfused arch ofthe vertebra {spina bifida cystica), (c) meningomyelocele-a protrusion ofthe spinal cord and the meninges, and {d) myeloschisis (rachischisis)-a cleft spinal cord caused by failure of neural folds to close. Lumbar spondylosis (ankylosis) is a degenerative joint disease affecting the lumbar vertebrae and intervertebral disks, causing pain, muscle weakness, and stiffness, sometimes with sciatic radiation resulting from nerve root pressure by associated protruding disks or osteophytes. Klippel-feil syndrome is a congenital defect manifested as a short, stiff neck resulting from reduction in the number of cervical vertebrae or extensive fusion of the cervical vertebrae. Arnold-Chiari (or ChiarO deformity is a congenital cerebellomedullary malformation in which the cerebellum and the medulla oblongata protrude down into the vertebral canal through the foramen magnum. Atlanta-occipital joint is a condylar synovial joint and is involved inflexion, extension, and lateral ftexion of the head. The atlantoaxial joints consist of two lateral plane joints and one median pivot joint (between the anterior arch of the atlas and the dens of the axis) and are involved in rotation of the atlas and head as one unit on the axis. Atlantoaxial dislocation (subluxation) frequently occurs after rupture of the cruciform ligament caused by trauma or rheumatoid arthritis. It may result from a congenital absence of the dens, a fracture of the dens, or direct trauma frequently caused by traffic accidents. Compression fracture is produced by collapse ofthe vertebral bodies resulting from trauma, infection, metastatic cancer and results in hyperkyphosis or scoliosis, and may cause spinal nerve compression. Whiplash injury of the neck is produced by a force that drives the body forward whereas the head lags behind, causing the head (with the upper part of the neck) to hyperextend and the lower pan of the neck to hyperflex rapidly, as occurs in rear-end automobile collisions. Herniated (slipped) disk is a protrusion of the nucleus pulposus through the annulus fibrosus of the intervertebral disk into the intervertebral foramen or into the vertebral canal, compressing the spinal nerve root. It commonly occurs posterolaterally. Sciatica is pain in the lower back and hip, radiating into the buttock and into the lower limb, and is most commonly caused by herniation of a lower lumbar intervertebral disk, compressing or irritating the roots of the sciatic nerve. It causes muscular weakness, numbness, tingling, and pain along the path of the sciatic nerve. Hangman fracture is a fracture ofthe pedicles ofthe axis ( C2), which may occur as a result of judicial hanging or automobile accidents. In this fracture, the cruciform ligament is tom, and the spinal cord is crushed by the dens, causing death. Spinal cord occupies approximately the upper two-thirds of the vertebral canal, is enveloped by three meninges, and has cervical and lumbar enlargements for nerve supply to the upper and lower limbs, respectively. It has a conical end, known as the conus medullaris, which terminates at the level ofL2 vertebra in adults. Denticulata ligaments are 21 pairs oflateral extensions of the pia mater; the filum terminals intemus is an inferior extension of the pia mater; CSF is formed by vascular choroid plexuses in the ventricles ofthe brain and is contained in the subarachnoid space; and the cauda aqui na (horse's tail) is formed by the dorsal and ventral roots of the lumbar and sacral spinal nerves. Tethered cord syndrome is caused by stretching of the caudal spinal cord as a result of congenital fixation of the spinal cord. It is characterized by an abnormally low conus medullaris, which is tethered by a short, thickened filum terminale, leading to conditions such as progressive neurologic defects in the legs and feet and scoliosis.

44

BRS Gross Anatomy Spinal nerves consist of31 pairs ofnerves (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and I coccygeal). The cervical spinal nerves exit above the correspondingly numbered vertebrae except the eighth cervical nerves, which emerge below the seventh cervical vertebra; the remaining spinal nerves exit below the correspondingly numbered vertebrae. Shi ogles (harpes zoster) is caused by the varicella zoster virus that remains latent in the dorsal root ganglia of spinal nerves and the sensory ganglia of cranial nerves. It results from activation of the virus, which travels down the sensory nerve to produce severe neuralgic pain, eruption of groups ofvesicles, or a rash in the dermatome of the nerve. Caudal (epidural) anesthesia is used to block the spinal nerves in Iha epidural space by injection of local anesthetic agents via the sacral hiatus located between the sacral comua. Spinal anesthesia is introduction of anesthetic into the dural sac and blocks neural transmission to all areas below the level of injection. Pudenda! anesthesia is the introduction of anesthetic into the pudenda! canal and provides pain relief in the perineal region. Lumbar puncture (spinal tap) ls the tapping of the subarachnoid space in the lumbar region (lumbar cistern), usually between the laminae ofvertebrae L3 and IA or vertebrae IA and LS. It allows measurement of CSF pressure and withdrawal of a fluid sample for microbial or chemical analysis and also allows introduction of anesthesia, drugs, or radiopaque material into the subarachnoid space. Meninges consist of a pia mater (innermost layer), arachnoid mater (transparent spidery layer), and dura mater (tough fibrous outermost layer). The subarachnoid space between the pia and the arachnoid mater contains CSF; the subdural space between the arachnoid and the dura mater contains moistening fluid; and the epidural space external to the dura mater contains the internal vertebral venous plexus. Meningitis is inflammation ofthe meninges caused by viral or bacterial infection. Bacterial meningitis (purulent meningitis) is an extremely serious illness and may result in brain damage or death, even if treated. Meningitis is also caused by fungi, chemical irritation or drug allergies, and tumors. Vertebral artery arises from the subclavian artery and ascends through the transverse forarnina of the upper six cervical vertebrae. Vertebral veins are fanned in the suboccipital triangle by tributaries from the venous plexus around the foramen magnum and the suboccipital venous plexus and descend through the transverse foramina. Internal vertebral venous plexus lies in the epidural space and communicates superiorly with the cranial dural sinuses and inferiorly with the pelvic veins and with both the azygos and caval systems in the thoracic and abdominal regions. This venous plexus is the route of early metastasis of carcinoma from the lung, breast, and prostate gland or uterus to the bones and the CNS. External vertebral venous plexus lies in front of the vertebral column and on the vertebral arch and communicates with the internal vertebral venous plexus. Superficial muscles of the back are involved in moving the shoulder and arm and are innervated by ventral primary rami of the spinal nerves. Intermediate muscles are muscles of respiration. Deep muscles of the back are responsible for extension of the spine and head and are innervated by dorsal primary rami of the spinal nerves. Triangle of auscultation is bounded bythelatissimus dorsi, trapezius, and scapula (medial border) and is the site where breathing sounds can be heard most clearly. The lumbar triangle is formed by the iliac crest, latissimus dorsi, and external oblique abdominal muscles. It may be the site of an abdominal hernia. Suboccipital triangle is bounded by the rectus capitis posterior major, obliquus capitis superior, and obliquus capitis inferior muscles. The suboccipital muscles are innervated by the suboccipital nerve (dorsalprimaryramus of Cl). Accessory nerve consists of a cranial portion that joins the vagus nerve and a spinal portion that supplies the sternocleidomastoid and trapezius muscles. Dorsal scapular nerve (C5) supplies the rhomboid major and minor and levator scapulae muscles. Subocc ipita I nerve (C1 )supplies the muscles of the sub occipital region. The greater occi pitaI nerve (CZ) is derived from the dorsal primary ramus and communicates with the suboccipital and third occipital nerves and may supply the semispinalis capitis.

Review Test

Directions: Bach of the numbered questions is followed by potential answers. Select the one-lettered answer 1hat is best in each case.

1. During an outbreak of meningitis at a local college, a 20-year-old student presents to a

4. A 39-year-old woman with headaches

hospital emergency department complaining of headache, feveJf chills, and stl.iI neck. He is about to get a lumbar puncture (spinal

back pain from a possible herniated disk.

tap). Cerebrospinal fiuid ( CSfl) is normally withdrawn from which of the following

spaces? (A) Epidural space

(B) Subdural space (C) Space between the spinal cord and the pia mater (D) Subaraclmoid space (E) Space between the arachnoid and the dura maters

presents to her primary care physician. with Her magnetic resonance imaging (MRI) scan

reveals that the posterolateral protrusion of the intervertebral disk betw~ the lA and L5 vertebrae would most Wcely a1Iect nerve roots from which of the following spinal nerves? IA) Third lumbar nerve IB) Fourth lumbar nerve IC) Fifth lumbar nerve ID) First sacral nerve IE) Second sacral nerve

5. A 57-year-old woman comes into her

l. A 23-year-old jockey falls from her horse and complains of headache, backache, and weakness. Radiologlc examination would reveal blood in which of the following spaces if the internal vertebral venous plexus was ruptured? (A) Space deep to the pla mater (B) Space between the arachnoid and the dura maters (C) Subdural space (D) Epidural space (E) Subaraclmoid space

physician's office complalnlng of fever, nausea, vomiting, and the worst headache of her life. Testa and physical examination suggest hydrocephalus (widening ventricles) resulting from a deaease in the absorption of CSP. A decrease of Dow in the CSP through which of the following structures would be responsible for these findings? IA) Choroid plems IB) Vertebral venous plems IC) Arachnoid villi ID) Internal jugular vein IE) Subarachnoid trabeculae

3. A 42-year-old woman with metastatic

6. After a 26-year-old man's car was broadsided

breast cancer is known to have tumors in the lntervertebral foramina between the fourth and fifth cervical vertebrae and between the fourth and fifth thoracic vertebrae. Which of the following spinal nerves may be damaged? (A) Fourth cervical and fourth thoracic nerves (B) Fifth cervical and fifth thoracic nerves (C) Fourth cervical and fifth thoracic nerves (D) Fifth cervical and fourth thoracic nerves (E) Third cervical and fourth thoracic nerves

by a large ttuck, he is brought to the emergency department with multiple fractures or the transverse processes or the cervical and upper thoracic vertebrae. Which of the following muscles might be a1Iected? IA) Trapezlus IB) Levator scapulae IC) Rhomboid major ID) Serratus posterior superior IE) Rectus capitis posterior major

45

46

BRS Gross Anatomy

1. A27-year-old mountain climber falls from a steep rock wall and is brought to the emergency department His physical examination and computed tomography (CT) scan reveal dislocation fracture of the upper thoracic vertebrae. The fractured body of the T4 vertebra articulates with which of the following parts of the ribs?

IAI IBI ICI ID I

Head of the third rib Neckofthefourthrib Tubercle of the fourth rib Head of the fifth rib IE) Tubercle of the fifth rib

8. A mother brings her young toddler to her pediatrician with new onset of bowel and bladder dysfunction and loss of the lower limb function. Her mother had not taken enough folic acid (to the point of deficiency) during her pregnancy. On examination, the child has protrusion of the spinal cord and meninges and is diagnosed with which of the following conditions?

IAI IBI IC) IDI

Spina bifida occulta Meningocele Meningomyelocele Myeloschisis IE) Syringomyelocele

9. A 34-year-old woman crashes into a tree during a skiing lesson and is brought to a hospital with multiple injuries that impinge the dorsal primary rami of several spinal nerves. Such lesions could affect which of the following muscles?

IA) IBI IC) ID I

Rhomboid major Levator scapulae Serratus posterior superior Iliocostalis IE) Latissimus dorsi

10. During a schoolyard fight, a 16-year-old boy suffers a deep stab wound near the superior angle of the scapula near the medial border, which compromises both the dorsal scapular and spinal accessory nerves. Such an injury could result in paralysis or weakness of which of the following muscles?

IA) IBI IC) IOI

Trapezius and serratus posterior superior Rhomboid major and trapezius Rhomboid minor and latissimus dorsi Splenius cervicis and sternocleidomastoid IE) Levator scapulae and erector spinae

11. An elderly man at a nursing home is known to have degenerative brain disease. When CSF is withdrawn by lumbar puncture for further examination, which of the following structures is most likely penetrated by the needle?

IAI IBI IC) ID)

Pia mater Filum terminale externum Posterior longitudinal ligament Ligamentum flavum IE) Annulus fibrosus

12. A 27-year-old stuntman is thrown out of his vehicle prematurely when the car used for a particular scene speeds out of control. His spinal cord is crushed at the level of the fourth lumbar spinal segment. Which of the following structures would most likely be spared from destruction?

IA) IBI ICI ID)

Dorsal horn Ventral horn Lateral horn Graymatter IE) Pia mater

13. A 24-year-old woman comes to the hospital to deliver her baby. Her obstetrician uses a caudal anesthesia during labor and childbirth to block the spinal nerves in the epidural space. Local anesthetic agents are most likely injected via which of the following openings?

IA) IBI ICI ID)

Intervertebral foramen Sacral hiatus Vertebral canal Dorsal sacral foramen IE) Ventral sacral foramen

14. In a freak hunting accident, a 17-year-old boy was shot with an arrow that penetrated into his suboccipital triangle, severing the suboccipital nerve between the vertebral artery and the posterior arch of the atlas. Which of the following muscles would be unaffected by such a lesion?

IAI IB) IC) ID)

Rectus capitis posterior major Semispinalis capitis Splenius capitis Obliquus capitis superior IE) Obliquus capitis inferior

l!iJtt:ltJij Back 15. A 26-year-old heavyweight boxer suffered a punch to his mandible, resulting in a slight subluxation (dislocation) of the atlantoaxial joint. The consequence of the injury was decreased range of motion at that joint. What movement would be most affected? (A) Extension (B) Flexion (C) Abduction (D) Adduction (E) Rotation

16. A crush injury of the vertebral column can cause the spinal cord to swell. Which structure would be trapped between the dura and the vertebral body by a swelling spinal cord? (A) Anterior longitudinal ligament (B) Alar ligament (C) Posterior longitudinal ligament (D) Cruciform ligament (E) Ligamentum nuchae

17. A44-year-old woman comes to her physician and complains of headache and backache. On examination, she is found to have fluid accumulation in the spinal epidural space because of damage to blood vessels or meninges. Which of the following structures has most likely ruptured? (A) Vertebral artery (B) Vertebral vein (C) External vertebral venous plexus (D) Internal vertebral venous plexus (E) Lumbar cistern

18. A 69-year-old man has an abnormally increased curvature of the thoracic vertebral column. Which of the following conditions is the most likely diagnosis? (A) Lordosis (B) Spina bifida occulta (C) Meningocele (D) Meningomyelocele (E) Kyphosis

19. During a snowstorm, a 52-year-old man is brought to the emergency department after a multiple car accident. Which of the following conditions is produced by a force that drives the body forward while the head lags behind in a rear-end automobile collision? (A) Scoliosis (B) Hangman fracture (C) Meningomyelocele

47

(DI Whiplash injury (El Herniated disk 20. A 37-year-old man is brought to the emergency department with a crushed second cervical vertebra {axis) that he suffered after a stack of pallets fell on top of him at work. Which of the following structures would be intact after the accident?

(Al Alar ligament (B) Apical ligament (C) Semispinalis cervicis muscle (DI Rectus capitis posterior minor (El Obliquus capitis inferior 21. A middle-aged coal miner injures his back after an accidental explosion. His MRI scan reveals that his spinal cord has shifted to the right because the lateral extensions of the pia mater were torn. The function of which of the following structures is most likely impaired?

(Al Filum terminale internum (B) Coccygeal ligament (C) Denticulate ligament (DI Choroid plexus (El Tectorial membrane 22. A 25-year-old man with congenital abnormalities at birth has a lesion of the dorsal scapular nerve, maldng him unable to adduct his scapula. Which of the following muscles is most likely paralyzed? (A) Semispinalis capitis (Bl Rhomboid major (C) Multifidus (DJ Rotator longus (El Iliocostalis

23. After an automobile accident, a 47-year-old man suffers an injury to a back muscle that forms the boundaries of the triangle of auscultation, and the lumbar triangle receives no blood. Which of the following muscles might be ischemic?

(A) Levator scapulae (BJ Rhomboid minor (C) Latissimus dorsi (DI Trapezius (El Splenius capitis

48

IRS Gross Anatemy

Z4. A 38-year-old woman with a long history of shoulder pain is admitted to a hospital for surgery. Which of the following mu$Cles becomes ischemic soon after ligation of the superfl.dal or ascending branch of the transverae cervical artery?

(A) Lattssimu• dorsi

a.

When the internal vertebral venous plems is ruptured, venous blood may spread into which tissue and space?

27. Dorsal and ventral roots of the lower lumbar and sacral nerves are lacerated. Which structure is moat likely damaged?

(B) Multliidu•

(C) Trapezlus (D) Rhomboidmajor (El Longiuimus capitil

25. A 25-year-old soldier suffers a gumhot wound on the lower part of his back and is unable to mtMl his legs. A neurologic examination and MRI scan reveal injury of the cauda equina. Which of the following is most lilc.ely damaged?

(A) Dorsal primary rami (B) Ventral primary rami (C) Dorsal roots of the thoracic spinal nerves (D) Ventral roots of the &acral spinal nerves (E) Lumbar spinal nerves

Questions 2& ta 30: Cllaase the appropriate lettllnid structur• in this MRI scan Gf tll• back (1ee Figu,. b•low).

28.

The spinal cord is crushed at the level of the upper part of the first lumbar vertebra. Which structure is most likely damaged?

29. Which structure may herniate through the annulus fibrosus, thereby impl.nging on the roots of the spinal nerve? 30. CSF is produced by vascular choroid plexuses in the ventricles of the brain and accumulated in which space?

Answers and Explanations 1. The answer is D. (Spinal Cord andAssodated Structures: IV.D) Cerebrospinal Duld (CSF) is found in the subarachnold space, which is a wide interval between the arachnoid layer and the p1a mater. The epidural space contains the internal vertebral venous pl.ems and epidural fat. The subdural space between the arachnoid and the dura contains a little Duid to moisten the meningeal surface. The pia mater closely covers 1he spinal cord and enmeshes blood vessels on 1he surfaces ofthe spinal cord. Thus, the space between the spinal cord and the pia is a potential space.

2. The answer i• D. (Spinal Cord and Associated. Structures: m.C) The space between 1he vertebral canal and 1he dura mater is the epidural space, which contains the internal vertebral venous plexus. The spinal cord and blood vessels lie deep to the pia mater. The space between the arachnoid and the dura maters is the subdural space, which contains a film offluid. The subarachnoid space contains CSP. 3. The answer i• D. (Spinal Cord and Associated. Structures: U) All cervical spinal nerves exit through the intervertebral foramina above the corresponding vertebrae except the eighth cervical nerves, which run inferior to the seventh cervical vertebra. All other spinal nerves exit the intervertebral foramina below the cOITesponding vertebrae. Therefore, the fifth cervical nerve p~ between the fourth and the 8fth cervical vertebrae, and the fourth thoracic nerve runs between the fourth and the fifth thoracic vertebrae. 4. The answer is C. (Vertebral Column; m:, Figure 2.5) Aposterolateral herniation of the intervertebral disk at disk. levels IA to LS affects the fifth lumbar nerve root but rarely affects the fourth lumbar nerve root because of a progressive d~cending obliquity of the fourth and the fifth lumbar nerve roots. The first seven cervical nerves exit above the corresponding vertebra, and the eighth cervical nerve exits below the seventh cervical vertebra because there are eight cervical nerves but only seven cervical vertebrae. The rest of the spinal nerves exit below thelr corresponding vertebrae. 5. The answer is C. (Spinal Cord and Associated. Structures: W.D) CSP ls absorbed into the venous system primarily through the arachnoid villi. projecting into the cranial dural venous sinuses, particularly the superior sagittal sinus. CSF is produced by the choroid plell:Wles of the ventricles of the brain and is circulated in the subaracbnoid space, in which subarachnoid traheculae are also found. The vertebral venous plems and internal jugular vein are not iD:volved in the absorption of CSP. &. The answer is B. (Structures of the Back: 'Thble 2.1) The levator scapulae arise from the transverse processes of the upper cervical vertebrae and insert on the medial border of1he scapula. The other muscles are attached to the spinous processes of the vertebrae. 1. The answer is D. (Vertebral Colwrm: Iv.B) The body of vertebra T4 articulat~ wi1h the beads of the fourth and fifth ribs. The body of the T3 vertebra artlculates with the head of the thlld and fourth ribs. The neck ofa rib does not articulate with any part of the vertebra. The transverse process of the vertebra articulates with the tubercle of the corresponding rib. Therefore, the transverse process of vertebra T4 articulates with the tubercle of the fourth rib. I. The answer is C. (Vertebral Column: 111.B, Clinical Correlates} Meningomyelocele is protrusion of the meninges and spinal cord through the unfused arch of the vertebra. Folic acid in sufficient amounts during pregnancy is shown to prevent 1hese kinds of neural tube derects. Spina bifida occulta is failure of the vertebral arch to fuse (only bony defect). Meningocele is protrusion of the meninges through 1he derective vertebral arch. Syringomyelocele is protrusion of the meninges and a pathologic tubular cavity in the spinal cord or brain. 9. The answer i• D. (Structures of the Back.: Il.A.2) The dorsal primaryrami of the spinal nerves innervate the deep muscles of the back, including the iliocostalis. The other muscles are the superficial muscles of the back, which are innervated. by the ventral primary rami of the spinal nerves. 49

50

BRS Gross Anatomy

10. The answer is B. (Structures of the Back: Table 2.1) The dorsal scapular nerve innervates the levator scapulae and rhomboid muscles, whereas the accessory nerve innervates the trapezius and stemocleidomastoid muscles. The serratus posterior superior is innervated by ventral pri· mary rami of the spinal nerves, whereas the splenius cervicis and erector spinae are innervated by dorsal primary rami of the spinal nerves.

11. The answer is D. (Spinal Cord and Associated Structures: m.B) The CSF is located in the subarachnoid space, between the arachnoid layer and the pia mater. In a lumbar puncture, the needle penetrates the skin, fascia, ligamentum flavum, epidural space, dura mater, subdural space, and arachnoid mater. The pia mater forms the intern.al boundary of the subarachnoid space; thus, it can· not be penetrated by the needle. The posterior longitudinal ligament lies anterior to the spinal cord; thus, it is not penetrated by the needle. The filum terminale extemum is the downward prolongation of the spinal dura mater from the second sacral vertebra to the dorsum of the coccyx. The annulus fibrosus consists of concentric layers of fibrous tissue and fibrocartilage surrounding and retaining the nucleus pulposus of the intervertebral disk, which lies anterior to the spinal cord.

12. The answer is C. (Spinal Cord and Associated Structures: II) The lateral horns, which contain sympathetic pregangllonic neuron cell bodies, are present between the first thoracic and the second lumbar spinal cord levels (Tl-L2). The lateral horns of the second, third, and fourth sacral spinal cord levels (S2-S4) contain parasympathetic pregangllonic neuron cell bodies. The entire spinal cord is surrounded by the pia mater and has the dorsal horn, ventral horn, and gray matter. Note that the fourth lumbar spinal cord level is not the same as the fourth vertebral level.

13. The answer is B. (Spinal Cord and Associated Structures: N.A) Caudal (epidural) anesthesia is used to block the spinal nerves in the epidural space by injecting local anesthetic agents via the sacral hiatus located between the sacral cornua. An intervertebral foramen transmits the dorsal and ventral primary rami of the spinal nerves. The vertebral canal accommodates the spinal cord. Dorsal and ventral sacral foramina transmit the dorsal and ventral primary rami of the sacral nerves.

14. The answer is C. (Structures of the Back: II.A.I) The splenius capitis is innervated by dorsal primary rami of the middle and lower cervical nerves. The suboccipital nerve (dorsal primary ramus of Cl) supplies the muscles of the suboccipital area, including the rectus capitis posterior major, obliquus capitis superior and inferior, and the semispinalis capitis.

15. The answer is E. (Soft Tissues of the Back: IIl.F.2) The atlantoaxial joints are synovial joints that consist of two plane joints and one pivot joint and are involved primarily in rotation of the head. Other movements do not occur at this joint.

16. The answer is C. (Vertebral Column: V.B) The posterior longitudinal ligament interconnects the vertebral bodies and intervertebral disks posteriorly and runs anterior to the spinal cord within the vertebral canal. The ligamentum nuchae is formed by supraspinous ligaments that extend from the seventh cervical vertebra to the external occipital protuberance and crest. The anterior longitudinal ligament runs anterior to the vertebral bodies. The alar and cruciform ligaments also lie anterior to the spinal cord.

17. The answer is D. (Vertebral Column: VI.A) The internal vertebral venous plexus is located in the spinal epidural space. The vertebral artery and vein occupy the transverse forarnina of the upper six cervical vertebrae. The external vertebral venous plexus consists of the anterior part, which lies in front of the vertebral column, and the posterior part, which lies on the vertebral arch. The lumbar cistern is the enlargement of the subarachnoid space between the inferior end of the spinal cord and the inferior end of the subarachnoid space.

18. The answer is E. (Vertebral Column: I, Clinical Correlates) Kyphosis (hunchback or humpback) is an abnormally increased thoracic curvature, usually resulting from osteoporosis. Lordosis is an abnormal accentuation of the lumbar curvature. Spina bifida occulta is failure of the vertebral arch to fuse (only bony defect). Meningocele is a protrusion of the meninges through the unfused arch of the vertebra, whereas meningomyelocele is a protrusion ofthe spinal cord and the meninges.

19. The answer is D. (Vertebral Column: II, Clinical Correlates) Whiplash injury of the neck is produced by a force that drives the trunk forward, whereas the head lags behind. Scoliosis is a lateral deviation resulting from unequal growth ofthe spinal column. Hangman fracture is a fracture ofthe neural arch through the pedicle of the axis that may occur as a result ofhanging or motor vehicle accidents.

l!iJtt:ltJij Back

51

Meningomyelocele is a protrusion of the spinal cord and its meninges. A herniated disk compresses the spinal nerve roots when the nucleus pulposus is protruded through the annulus fibrosus.

20. The answer is D. (Structures of the Back: Table 2.2 and III.G) The rectus capitis posterior minor arises from the posterior tubercle of the atlas and inserts on the occipital bone below the inferior nuchal line. The alar ligament extends from the apex of the dens to the medial side of the occipital bone. The apical ligament extends from the dens of the axis to the anterior aspect of the foramen magnum of the occipital bone. The semispinalis cervicis arises from the transverse processes and inserts on the spinous processes. The obliquus capitis inferior originates from the spine of the axis and inserts on the transverse process of the atlas.

21. The answer is C. (Spinal Cord and Associated Structures: III.A) The denticulate ligament is a lateral extension of the pia mater. The filum tenninale (intemum) is an inferior extension of the pia mater from the tip of the conus medullaris. The coccygeal ligament, which is also called the filum terminale externum or the filum of the dura, extends from the tip of the dural sac to the coccyx. The vascular choroid plexuses produce the CSF in the ventricles of the brain. The tectorial membrane is an upward extension of the posterior longitudinal ligaments from the body of the axis to the basilar part of the occipital bone.

22. Tha answer is B. (Structures of the Back: I, Table 2.1) The rhomboid major is a superficial muscle of the back; it is innervated by the dorsal scapular nerve, which arises from the ventral primary ram us of the fifth cervical nerve, and adducts the scapula. The semispinalis capitis, multifidus, rotator longus, and iliocostalis muscles are deep muscles of the back, are innervated by dorsal primary rami of the spinal nerves, and have no attachment to the scapula.

23. The answer is C. (Structures of the Back: I.A and Table 2.1) Thelatissimus dorsiforms boundaries of the auscultation and lumbar triangles and receives blood from the thoracodorsal artery. The levator scapulae, rhomboid minor, and splenius capitis muscles do not form boundaries of these two triangles. The trapezius muscle forms a boundary of the auscultation triangle but not the lumbar triangle. The levator scapulae, rhomboid minor, and trapezius muscles receive blood from the transverse cervical artery. The splenius capitis muscle receives blood from the occipital and transverse cervical arteries.

24. The answer is C. (Structures of the Back: I.C.2) The trapezius receives blood from the superficial branch of the transverse cervical artery. The latissimus dorsi receives blood from the thoracodorsal artery. The rhomboid major receives blood from the deep or descending branch of the transverse cervical artery. The multifidus and longissimus capitis receive blood from the segmental arteries.

25. Tha answer is D. (Spinal Cord and Associated Structures: Iv.A) The cauda equina is the collection of dorsal and ventral roots of the lower lumbar and sacral spinal nerves below the spinal cord. Dorsal and ventral primary rami and dorsal roots of the thoracic spinal nerves and lumbar spinal nerves do not participate in the formation of the cauda equina.

26. Tha answer is E. {Spinal Cord and Associated Structures: 111.C) Epidural fat is shown in the magnetic resonance imaging scan. In addition, the internal vertebral venous plexus lies in the epidural space; thus, venous blood from the plexus may spread into epidural fat.

27. The answer is C. (Spinal Cord and Associated Structures: IV.A) The cauda equina is fanned by a great lash of the dorsal and ventral roots of the lumbar and sacral nerves.

28. Tha answer is B. (Spinal Cord and Associated Structures: I) The conus medullaris is a conical end of the spinal cord and terminates at the level of the L2 vertebra or the intervertebral disk between the Ll and L2 vertebrae. A spinal cord injury at the level of the upper part of the first lumbar vertebra damages the conus medullaris.

29. Tha answer is A. (Vertebral Column: III) The intervertebral disk lies between the bodies of two vertebrae and consists of a central mucoid substance, the nucleus pulposus, and a surrounding fibrous tissue and fibrocartilage, the annulus fibrosus. The nucleus pulposus may herniate through the annulus fibrosus, thereby impinging on the roots of the spinal nerves.

30. Tha answer is D. (Spinal Cord and Associated Structures: Iv.D) The CSF is found in the lumbar cistern, which is a subarachnoid space in the lumbar area. CSF is produced by vascular choroid plexuses in the ventricles of the brain, circulated in the subarachnoid space, and filtered into the venous system through the arachnoid villi and arachnoid granulations.

Thorax

THORACIC WALL I. SKELETON OF THE THORAX (see Figure 3.1) A. Sternum ■ Is a flat bone in the anterior chest wall and consists of them nd the xiphoid process. Its body is more than twice as long as the rnanubriurn in the mal of the rnanubrium in the female. 1. Manubrium The superior margin contains the jugul be readily palpated at the root of the neck. Has a clavicular notch on each side for artiwlaf o with the clavicle. ■ Also articulates with the cartilage of the first rib, the upper half of the second rib, and the body of the sternum at the manubfioster al j(')int, or sternal angle. 2. Sternal angle (angle of Louis) Is the junction between the manuorium and the body of the sternum. Is located at the level whe e (a) The second ribs articulate with the sternum. (b) The aortic arch oegins and ends.

Manubrium of sternum Transverse process - - ~ ~ - - ~_A Inferior costal facet - - - - - - + - - - ' . - - - - - - - " - s - - ~

\ Body of sternum

Xiphoid process of sternum

FIGURE 3.1. Articulations ofthe ribs with the vertebrae and the sternum.

52

l3lit22J Thorax

53

(c) The ttachea bifurcates into the right and left bronchi at the carina. (d) The inferior border of the superior mediastinum is demarcated. (e) A transverse plane can pass through the intervertebral disk between T4 and T5. 3. Body of the sternum Articulates with the second to seventh costal. cartilages. The xiphisternal ioint between the body and the :lipboid process lies at the T9 vertebral. level.

4. Xiphoid process Is a flat, cartilaginous process at birth that ossifies slowlyfrom the central core and unites with the body of the stemum after middle age. Ends at the TlOvertebral level, which marks the lower limitofthe thoracic cavity anteriorly, and the level of the esophageal hiatus in the diaphragm. Can be palpated in the epigastrium and is attached via its pointed caudal end to the lineaalba.

CUNICAL CORRELATES

The stemum is a possible site for bone marrow biopsy because it possesses hematopoietic marrow throughout life and beca use of its shallow depth and subcutaneous position. It may be split in the median plane (median stemotomy) to allow the surgeon to gain easier access to the lungs, heart. and great vessels.

B. Ribs Consist of 12 pairs of bones 1hat form the main part of1he bony daoracic wall, extending from the vertebrae posteriorly to or toward the sternum anteriorly. Increase the anteroposterior and transverse diameten of the thorax by their movements. 1. Structure Typical ribs are ribs 3 through 9, each of which has a head, neck, tubercle, and body {shaft). The h11d articulates with the corresponding vertebral bodies and intervertebral disks and supraadjacent vertebral bodies. The body (shaft) is 1hln and fiat and turns sharply anteriorly at the angle; it has a costal groon that follows the inf"erlor and internal surface of the rib and shields the intercostal vessels and nerves from injury. The tubercle articulates with the transverse processes of the corresponding vertebrae, except ribs 11 and 12. 2. Classification True ribs are the first seven ribs (rills 1-7t which are attached to the sternum by their oostal cartilages. False ribs are the lower five rlbs (ribs 1-12); ribs 8 to 10 are connected to the costal cartilages immediately above, and thus, the 7th to 10th costal cartilages form the anterior coital arch or costal margin. Roating ribs are the last two ribs (ribs 11 and 12), which are connected only lD the vertebrae.

CUNICAL CORRELATES

Tborecic outlet syndrome (TOS) occurs with compression of neurovascular structures in the thoracic outlet (a space between the clavicle and the first rib). A combination of pain, numbness, tingling, or weakness and fatigue in the upper arm is caused by pressure on the brachia! plexus (lower trunk or C8 and T1 nerve roots). Compression of the subclavian artery in the thoracic outlet results in ischemic muscle pain in the upper limb. One ca use of TOS is the presence of a cervical rib, a mesenchymal or cartilaginous elongation of the transverse process of the seventh cervical vertsbra. Compression of the naurovascular bundle may also occur as a result of first rib bony anomalies or abnormal insertions of the anterior and middle scalene musclas on the first rib, resulting in a particularly narrow space batween the two muscles.

54

BRS Graa Allatamy

CLINICAL CORRELATES

Flail chest is a loss of stability of the thoracic caga that occurs when a segment of the anterior or lateral thoracic wall moves freely because of multiple rib fractures, allowing the loose segment to move inward on inspiration and outward on expiration. Reil chest is an extremely painful injury and impairs ventilation, thereby affecting blood oxygen levels and causing respiratory failure. Rib fractures: Fracture of the first rib may injure tha brachia! plexus and subclavian vessels. The middle ribs are most commonly fractured and usually result from direct blows or crush injuries. The broken ends of ribs may cause pneumothorax and/or lung or spleen injury. Lower rib fractures may tear the diaphragm, resulting in a diaphragmatic hernia.

3. Fil'lt rib •

• •

Is the broadest and sharllll of the true ribs. Has a single articular facet on its head, which articulates with the first thoracic vertebra. Hes a scelana tubercla for the insertion of the anterior scalene muscle and two graovas for the subclavian artery and vein.

4. Second rib •

Has two articular facets on its head, which articulate with the bodies of the first and

second thoracic vertebrae. • Is about twice as long es the first rib. 5. Tenth rib • Has a single articular facet on its head, which articulates with the 10th thoracic vertebra. &. Eleventh and 12th ribs • Have a single articular facet on their heads. •

Have no neclc or tubercle.

II. ARTICULATIONS OF THE THORAX (see Figure 3.1) A. Starnoclavicular joint • Is a saddle-type synovial joint with two separate synovial cavities and provides the only bony attachment between the appendicular and aDal skeletons.

B. Starnocoml (stamochandral) joints • Are the articulation ofthe sternum with the first seven rib cartilages. The sternum (manubrium) fonns a synchondrosis with the first costal cartilage, whereas the second to seventh costal cartilages form synavial plane joints with the sternum.

C. Corlochondral joints • Are synchondroses in which the ribs articulate with their respective costal cartilages.

D. Manubriastamal joint • Is a symphysis (secondary cartilaginous joint) between the manubrium and the body ofthe sternum..

E. Xiphislemal joint • Is a synchondrosis articulation between the xi.phoid process and the body of the stemwn.

F. CorloY1rlebral joints • Are synovial plane joints of heads of ribs with corresponding and supraadjacent vertebral bodies.

G. Cortotransver11 joint • Is a synovial plane joint ofthe rib tubercle with the transverse process ofcorresponding vertebra.

H. lnt1rchondral joints • Are synovial plane joints between the 6th and the 10th costal cartilages of ribs.

l3JlJt!Jill Thorax

55

Ill. BREASTS AND MAMMARY GLANDS (see Figure 7.10)

IV. MUSCLES OF THE THORACIC WALL (see Table 3.1)

V. NERVES AND BLOOD VESSELS OF THE THORACIC WALL A. lntercastal nerves • Are the ventral primary rami of the first 11 thoracic spinal nerves. The ventral primary ramus of the 12th thoracic spinal nerve is the subcostal nene, which runs beneath the 12th n'b. • Run between the internal and the innennost layers of muscles, with the intercostal veins and arteries above (VAN is a mnemonic to remember the order from superior to inferior: veins, arteries, nerves). • Reside in the costal grooves on the inferior surface of the rib&. • Give rise to lateral and anterior cutaneous branches and muscular branches.

B. Intimal thoracic arl9ry • Usually arises from the first part of tha subclnian artery and descends directly behind the first six costal cartilages, just lateral to the sternum bilaterally.

• Gives rise to two anterior intercostal arteries in each of the upper six intercostal spaces and terminates at the sDrth intercostal space by dividing into the musculophrenic and superior epigastric arteries.

1. Pericardiophrenic arteri11 • •

Accompany the phrenic nerves between the pleura and the perica.nilum to the diaphragm. Supply the pleura, pericardium, and diaphragm (upper surface).

2. Anterior intercostal arteries •

Are 12 small artarias, 2 in each of the upper 6 intercostal spaces that run laterally, one each at the upper and lower borders of each space. The upper artery in each intercostal space anastomoses with the poltllrior intercolbll artery, and the lower one joins the collateral branch of the posterior intercostal artery.

•

Provide muscular branches to the intercostal, serratus anterior, and pectoral muscles.

t a b I e

3.1

Muscles of the Thoracic Wall

Mu1ei.

Orqin

ln1&rtian

Nam

At:tia1

External intarcostals

Lower border of ribs

Int•re Dstal

Elevate ribs in inspiration

lntamel intarcostals

Lower border of ribs

Uppar border of rib below Upper border of rib below Upper border of rib below Inner surface of costal cartilagasH

lntercostal lntere Dstal

Depress ribs lcostal part!: elevate ribs linterchondral partl Elevelll ribs

lntercostal

Depresses ribs

Upper borders ofribs 2 or3below Subjacent ribs between tubercle and angle

lntere ostal

Elevates ribs

Innermost intarcDstals Lower border of ribs Tnmsversus thoracis

Subcostalis Levator costarum

Posterior surface of lower rtamum and xiphoid Inner surface of lower ribs near their angles Transverse processes ofTI-Tll

Dorsal primary Elevates ribs rami of CB-TI 1

BRS Graa Allatamy

56

3. Antarior perforating branches •

•

Perforate the internal intercostal muscles in the upper sixintercostal spaces, course with the anterior cutaneous branches ofthe intercostal nerves, and supply the pectoralis major muscle and the skin and subcutaneous tissue over it. Provide the medial mammary branches {second, third, and fourth branches).

4. Musculophrenic artery • •

•

Follows the costal arch on the inner surface of the costal cartilages. Gives rise to two anterior arteries in the seventh, eighth, and ninth intercostal spaces; perforates the diaphragm; and ends in the 10th intercostal space, where it anastomoses with the deep circumflex iliac artery. Supplies the pericardium, diaphragm, and muscles of the abdominal wall

5. Superior apigallric artery • •

Descends on the deep surface of the rectus abdominis muscle within the rectus sheath; supplies this muscle and anastomoses with the inferior epigutric artery. Supplies the diaphragm, peritoneum, and anterior abdominal wall.

C. lntemal 1haracic vein • Is formed by the confluence of the superior epl.gastrl.c and musculophrenic veins, ascends on the medial side of the artery, receives the upper six anterior intercostal and pericardiophrenic veins, and ends in the brachiocephalic vein.

D. Thoracoapigalb'ic vein • Is a venous connection between the lateral thoracic vein and the superficial eplgastrlc vein.

VI. LYMPHATIC DRAINAGE OF THE THORAX A. Sternal or parasternal lintarnal thoracic! nodes • Are located along the internal thoracic artery. • Receive lymph from the medial portion of the breast, anterior intercostal spaces, diaphragm, and supraumbilical region of the abdominal wall • Drain into the junction of the internal jugular and subclavian veins.

B. lntercoltll nodn • Lle near the heads of the ribs in the posterior thoracic wall. • Receive lymph from the intercostal spaces and the pleura. • Drain into the cistema chyli or the thoracic duct.

C. Pllranic nodas • Lle on the thoracic surface of the diaphragm. • Receive lymph from the pericardium, diaphragm. and liver. • Drain into the parasternal and posterior mediastinal nodes.

VII. THYMUS • Is a bilobed structure, lying in the neck anterior to the trachea and just deep to the sternum in the superior mediastinum; attains its greatest relative size in the neonate, playing a key role in the development of the immune system in early life, but continues to grow until puberty and then undergoes a gradual involution, in which the thymic tissue is replaced by fat. Precursors of both B cells and T cells are produced in the bone marrow. T-lymphocyte precursors migrate to the thymus, where they develop into T lymphocytes. After the thymus undergoes involution, T lymphocytes (thymocytes) migrate out of the thymus to the peripheral lymphoid organs such as spleen, tonsils, and lymph nodes, where they further differentiate into mature inununologically

~ Thorax

57

competent cells, which are responsible for cell-mediated immune reactions. (In contrast, B-lympbocyte precursors remain in the bone marrow to develop into B lymphocytes, which migrate to the peripheral lymphoid organs, where they become mature lmmunocompetent B cells, which are responsible for the humeral Immune response. Also, B cells dliJerentiate into plasma cells that synthesize antibodies limmunoglobulins].) • Arises from the thirdpharyngeal pouches, is supplied by the inferior thyroid and internal thoracic artery, and produces a hormone, thymosin, which promotes T-lymphocyte dliJerentiation and maturation.

VIII. DIAPHRAGM AND ITS OPENINGS (see Figure 4.18)

MEDIASTINUM. PLEURA. AND ORGANS OF RESPIRATION

I. MEDIASTINUM (see Figure 3.2) Is an intarpleural spaca (area between the pleural cavities and lungs) in the thorax and is bounded laterallyby the pleural cavities, anteriorlyby the sternum and the transversus thoracis muscles, and posteriorly by the vertebral column. • Consists of the superior mediastinum superior to the pericardium and three inferior divisions: anterior, middle, and posterior.

A. Superior madiastinum • Is bounded superiorly by the oblique plane ofthe first rib and inferiorlyby the imaginary line running from the sternal angle to the lntervertebral disk between the fourth and fifth thoracic vertebrae. • Contains the superiorvena cava {SVC), brachiocephalic veins, arch of tile aorta, thoracic duct,

b'achea, esophagus, vagus nerve, left recurrent laryngeal nerve, and phreni.c nerve. • Also contains the thymus, which ls a lymphoid organ; Is the site at which immature lymphocytes develop into T lymphocytes; and secretes thymic hormones, which cause T lymphocytes to gain immunocompetence. It begins involution after puberty.

B. Anterior madiallinum • Ues anterior to the pericardium and posterior to the sternum and the transverse thoracic muscles. • Contains the remnants of the thymus gland, lymph nod.es, fat, and connective tissue.

Xiphoid process

RGURU.2. Madiastinum.

58

BRS Grass Anatomy

C. Middle mediastinum • Lies between the right and the left pleural cavities. Contains the heart. pericardium, phrenic nerves, roots of the great vessels (aorta, pulmonary arteries and veins, and venae cavae), arch of the azygoa Ylin, and main bronchi. D. Postarior madiastinum (saa Structures in the Posterior Madiastinum) Lies posterior to the pericardium between the mediasttnal pleurae. • Contains the esophagus, thoracic aorta, azygos and hemiazygos veins, thoracic duct. vagus nerves, sympathetic trunk, and splanchnic nerves.

II. TRACHEA AND BRONCHI (see Figure 3.3) A. Trachea • Begins at the inferior border of the cricoid cartilage (CS) as a continuation of the 1arym: and bifurcates into the right and left main stem bronchi at the level of the sternal angle. Is approximately 12 cm in length and has 16 to .2'I incomplete hyaline cartilaginous rings that open posteriorly toward the esophagus that prevent the trachea from collapsing. May be compressed by an aortic arch aneurysm, goiter, or thyroid tumor, causing dyspnea. The Carina is adownwanl and backwanl projection oftirelast tracheal cartilage, which lies at the levelof thestemalangleandformsakeel-lfkeridgeseparatingth.eopeningsoflherlghtandleftmainbronchi

Superior lobar bronchus

~!£'-;~~-Superior """1~~~ Inferior

'"'";;;;~~~~-Anteromedlal

Inferior lobar bronchu

basal ~~~~~~-Lateral bBSel

Posterior basal Medial base.I

RGUREU. Anterior view oftha trachea, bronchi, and lungs.

Inferior lobar bronchus

l31IJ.lD1I Thorax

59

• Bronchial dilation is mediated by sympathetic nerves, and bronchial constriction is via parasympathetic nerves. Carina may be distorted, widened posteriorly, and immobile in the presence of a bronchogenic carcinoma. The mucous membrane over the carina is one of the most sensitive areas of the tracheobronchial tree and is associated with the cough reflex.

B. Right main (primary) bronchus • Is shortar, wider, and more wartical than the left main bronchus; therefore, more foreign bodies that enter through the trachea lodge in this bronchus or the rlght Inferior lobar bronchus. • Runs under the arch of the azygos vein, divides into 3 lobar or secondary bronchi (superior, middle, and inferior) and finally into 10 segmental bronchi. The rlght superior lobar (secondary) bronchus is known as the eparttrial (above the artery) bronchus because it passes above the level of the pulmonary artery. All others are the hypartarial bronchi. C. Left main (primary) bronchus Runs inferolaterally inferior to the arch af the aorta, crosses anterior to the esophagus and thoracic aorta, and divides into Z lobar or secondary bronchi, the upper and lower; and finally into 8 to 10 segmental bronchi. Is also crossad superiorly by lhurch of Iha aorta over its proidm.al part and by Iha left pulmonary artary over its distal part.

CUNICAL

Chronic obstructive pulmonary diSBase (CUPD) is a group of lung disaasas associated with chronic obstruction of airflow through the airways and lungs such as chronic bronchitis and emphysema, which are the most common forms and are caused primarily by cigarette smoking. Symptoms of COPD include chronic cough, difficulty in breathing, chronic sputum production, and wheezing. It is treated with bronchodilators and glucocorticoids. Chronic bronchitis is an inflammation of the airways, which results in excessive mucus production that plugs up the airways, causing a cough and breathing difficulty. Emphyuma is an accumulation of air in Iha tanninal bronchiolea and alveolar 11cs (air is trapped in the lungs) caused by destruction af the alveolar walls, which decreases compliance and elasticity of lung tissue. This reduces the ability to move air and exchange oxygen and carbon dioxide, thereby reducing oxygen absorption. Barrel chest is a chest resembling the shape of a barrel, with increased anteropostarior diametarthat occurs as a result of long-term ovarinflation of the lungs, sometimes seen in cases of emphysema or asthma.

CORRELATES

CUNICAL CORRELATES

Asthma is chronic inflammation of the bronchi that causes swelling and narrowing (constriction) of the airways. It causes airway obstruction and is characterized by dyspnea (shortness of breath), cough, and wheezing because of spasmodic contraction of smooth muscles in the bronchioles. Bronchiectasi1 is chronic dilation of bronchi and bronchioles resulting from destruction of bronchial elastic and muscular elements, which may cause collapse afthe bronchioles. It may be caused by pulmonary infections (e.g., pneumonia, tuberculosis (TB]) or by bronchial obstruction with heavy sputum production. Signs and symptoms include chronic cough with expectoration of large volumes of sputum.

Ill. PLEURAE AND PLEURAL CAVITIES (see Figures 3.4 and 3.5) A. Pleura • Each lung is covered by a thin serous membrane called the visceral pleura, which is continuous with a serous membrane lining the thoracic wall and mediastinum, called the parietal pleura.

60

BRS Grass Anatomy Heart

\

I ''~---Parletal

pleura

"~---1eural cavity

_._+-Vlaceral pleura

Medlastlnal pleura------...

-----r-+-Pericardium Costodiaphregmatic recess

Diaphragm RGURU.4. Frontlll se c1i on of the 111orax.

·""~-Parietal

Azygosvein-f-P..~~-----\o+e

pleura

---Pleural cavity

Aorta -+-ltl-iW------l~mi Esophagus -t-fli-------;;i~'-\.'1!11)

Visceral pleura Gl"ll"""°---+1~1--Leftph~n~nerve

Right phrenlc nerve -t--9-l~-----1,.,_,..

-ffl'f-J--Left lung

Right lung---l~~1.--

11-----.~Yff--Medlasdnal

pleura

'-~~5'41111~---Costalp~ura

~~~v Costomedlasdnal 111Cess Heart

RGURE3.5. Horizontal 11ction through the thorax.

1. Parietal pleura •

•

• • •

Lines the inner surface of the thoracic wall and the mediastinum.. Different regions of the parietal pleura are named based on location. Tiie internal thoracic wall and vertebral bodies are covered by the costovertebral pleura, the thoracic surface of the diaphragm. by the diaphragmatic pleura, and the lateral boundary ofthe mediastinum ill linedby the medi1stin1I pleura. The cervical pleura (cupulal is a dome ofpleurathat projects into the neck above the neck ofthe first nb to cover the apex of the lung. Cervical pleura is reinforced by a suprapleural membrane (Sibson fascia), which is a thickening ofthe endotharacic fascia, and ill attached to the first rib and the transverse process ofthe seventh cervical vertebra. The parietal pleura is separated from the thoracic wall by the endothoraclc fascia, which is an ext:rapleural fascial sheet lining the thoracic wall. Intercostal n11Y11 innervate the costal pleura and the peripheral portion of the diaphragmatic pleura; phrenic nenes innervate the central portion of the diaphragmatic pleura and the mediastinal pleura. The parietal pleura ill nry sensitive to pain. Is supplied by branches of the internal thoracic, superior phrenic, posterior intercostal, and superior intercostal arteries. The veins from the parietal pleura join systemic veins. The mediastinalplewa emnds from the hilum inferiorlyto form the pulmonary ligament, a two-layered vertical fold ofthe parietal pleura. It reaches along the mediastinalsurface ofeach lung from the hilus to the base (diaphragmatic surface) and ends in a free falcifonn border. It suppom the lungs in the pleural sac by retaining the lower parts of the lungs in position.

l3lit22J Thorax

61

2. Visceral pleura (pulmonary pleura) Adheres to the surface of the lun~ and dips Into all of the fissures. lt is supplied by bronchial arteriea and drained by puhnonary veins. Visceral pleura is insensitive to pain but is sensitive to stretch and contains vasomotor fibers and sensory endings ofvagal origin, which maybe involved in respiratory reDees.

CUNICAL

Pleurisy (pleuritis) is an inflammation of the pleura with exudation (asca pa of fluid from blood vessels} into its cavity, causing the pleural surfaces to be roughened. This roughening produces friction, and a pleural rub can be heard with the stethoscope on respiration. The exudate forms dense adhesions between the visceral and the parietal pleurae, forming pleural adhesions. Symptoms include fever, chills, and dry cough. Treatments include relieving pain with analgesics, removal of fluid by pleuracentesis, and lidocaine for intercostal nerve block.

CORRELATES

B. Pleural cavity Is a potential space between the parietal and the visceral pleurae. Represents a closed sac with no communication between the right and the left parts. Coiltainsafilm.offiuid1hatlubricatesthesurfaceof1hepleuraeandfacilitates1hemovementof1helungs. 1. Co11odiaphragmatic rece1111 Are the pleural recesses formed by the reOection of the costal and diaphragmatic pleurae beyond the inf-erior margin of the lung. Can accumulate fluid when in the erect position. Allow the lungs to be pulled down and expanded during Inspiration. 2. Costomediminal rac81181 Are part of the pleural cavity where the costal and medlastinal pleurae meet anteriorly behind the stemum.

CUNICAL

Pneumothorax is an increase in air within the pleural cavity, which causes an increase in intrapleural pressure and subsequent loss of negative pressure, which leads to lung Cilllapsa. It results from an injury to the thoracic wall or the lung. TMSian pna•othorax is a life-threatening pneumathorax in which air enters during inspiration and is trapped during expiration; therefore, the resultant increased pressure displaces the mediastinum tu the opposite side, with consequent cardiopulmonary impairment Major symptllml of pneumothorax are chest pain and dyspnea. It can be trelltad by draining the pleural air collection by needle aspiration or chest tube thoracostomy.

CORRELATES

CUNICAL

Pleural effusion is an abnormal accumulation offluid in the pleural space. There are two types of pleural effusion: transudate (clear watery fluid) and exudate (cloudy viscous fluid). A 11'1nsudate is caused by congestive heart failure or. less commonly, liver or kidney disease, whereas an exudate is caused by inflammation, pneumonia, lung cancer, TB, asbestosis, or pulmonary embolism. Symptoms include shortness of braath, chest pain, and cough. It can be treated by removing fluid bythoracentesis and/or treating inflammation.

CORRELATES

CUNICAL

Tboracentt1i1 {pleuracente1i1 or pleural tap) is surgical entry through the thoracic wall into the pleural cavity for aspiration of fluid. An accumulation of fluid in the pleural cavity is known by clinical names, such as a hydrothorax (water), a ll•othorax (blood), a chvlodlorax {lymph), and a pyodlorax {pus). It is performed at or posterior to the midaxillary line, one or two intercostal spaces below the fluid level but not below the ninth intercostal space. (The ideal site is the seventh, eighth, or ninth intercostal space, as this site avoids possible accidental puncture of the lung, liver, spleen, and diaphragm.) A needle should be inserted immediately above the superior margin at a rib to avoid injury to the intercostal naurovascular bundle, which travels in a notch below each rib.

CORRELATES

&2

BRS Graa Allatamy

IV. LUNGS (see Figures 3.3 and 3.6) • Are the 1111ntial organs of re1piralion and are attached to the heart and trachea by their roots and the pulmonary ligaments, respectively. • Contain nonrespiratory tissues, which are nourished by the bronchial arteri11 and drained by the bronchial veins for the larger subdivisions ofthe bronchi, and bythe pulmonarr veins for the smaller subdivisions of the bronchial tree. • Have b1111 that rest on the convex surface of the diaphragm, descend during inspiration, and ascend during e:1piration. • Receive parasympathetic fibers that innervate the smooth muscle and glands of the bronchial tree and are predominantly excitatory to these structures (bronchoconstriction and secretomotor). Receive sympathetic fibers that innervate blood vessel&, smooth muscle, and glands ofthe bronchial tree and are lnhlbitory to these structures (bronchodilation and vasoconstriction). • Have some sensory endings ofvagal origin, which are stimulated by the stretching ofthe lung during inspiration and are concerned in the reilex control of respiration.

A. Right lung • Has an apex that projects Into the neck and a concave base that slts on the diaphragm. • Is larger and heavier than the left lung, but is shorter and wider because ofthe higher right dome of the diaphragm and the inclination of the heart to the left. • Is dMded into superior, middle, and inferior lobes by the oblique and horizontal (accessory) fissures, but usually receives asingle bronchial artery. The oblique fiuure begins posteriorly at the head of the fifth rib and follows roughly the line of the sixth rib. The horizontal fissure runs from the oblique fissure in the midaxillary line at the sildh rib level and extends forward to the fourth costal cartilage level. • Has 3 lobar (secondary) bronchi and 10 segmental (tertiary) bronchi. • Has grooves for various structures (e.g., SVC, arch of azygos vein, esophagus).

D Upperlobe D Middle lobe D Lower1obe

Anterior lung fields

Posterior lung fields

RGURE3.8. The position of lung lobes in relation 1D the ribs, vertebrae, and intllrcostal spaces.

l3lit22J Thorax

63

B. Lift lung Is divided into superior and inferior lobes by an oblique fissure that follows the line of the s1xth rib, la usually more vertical in the left ltmg than in the right IWlg, and usually receives two broncbial arteries. Contains the lingula, a tongue-shaped portion of the superior lobe that corresponds to the middle lobe of the right lung. Contains a cardiac imprtnion, a cardiac notch (a deep indentation ofthe anterior border ofthe 1uperior lobe of the left lung), and groovH for various structures (e.g., aortic arch, descending aorta, left subcla:vian artery). Has 2 lobar (secondary) bronchi and 8 to 10 segmental bronchi.

C. Lung auscultation (see Figure 3.6) It is cllnlcally important to visualize the position of the 5 lung lobes on the thoracic wall to un-

derstand auscultation findings. The left and right upper lobes project to the anterior cheat wall. The lower lobes of both lungs have very little projection anteriorly, but are overrepresented on the back of the thoru. The middle lobe of the right lung projects anteriorly and laterally. To summarize, sounds heard anteriorly, think upper lobes; fur lower lobea, listen posteriorly; the middle lobe will be heard to the right. near the midaxlllary line.

CUNICAL CORRELATES

Pneumonia (pneumonitis) is an inflammation of the lungs from chemical, infectious, or autoimmune disease. It is an infection of the lungs that may be of bacterial, viral, or fungal origin. Symptoms are usually cough, fever, sputum production, chest pain, and dyspnea. Pneumonias are treated by administering antibiotics for infections, and pneumonitis is treated with anti-inflammatory agents such as steroids. TB is a lung infection caused by the bacterium MycohderiMI talHna/aisand is characterized by the formation of tubercles that can undergo caseous necrosis. Its symptoms are cough, fever, sweats, fatigue, and emaciation. TB is spread from an infected patient coughing and inhalation of these airborne particles by another individual. It can be treated with very effective drugs but usually requires four or more medications in view of increasing resistance.

CUNICAL CORRELATES

Pancoast or superior puhnon11Y sulc111Umor is a malignant neoplasm of the lung apex and causes Pancoast syndrome, which comprises (a) lower trunk brachia! plexopalhy(which causes severe pain radiating toward the shoulder and along the medial aspect of the arm and atrophy of the muscles of the forearm and hand) and (b) l11ion1 of cervical sympathtrtic chain ganglia with Homer syndrome (ptosis, enophthalmos, miosis, anhidrosis, and vasodilation). Superior pulmonary sulcus is a deep vertical groove in the posterior wa 11 of the thoracic cavity on either side of the vertebra I column formed by the posterior curvature of the ribs, lodging the posterior bulky portion of the lung.

CUNICAL CORRELATES

Pulmona1Y edema involves fluid accumulation and swelling in lung tissue or parenchyma, caused by infections and toxins causing altered capillary permeability, mitral stenosis, or left ventricular failure, which results in increased pressure in the pulmonary veins. As pressure in the pulmonary veins rises, fluid is pushed into Iha alveoli and becomes a barrier to normal oxygen exchange, resulting in shortness of breath. Signs and symptoms include rapid breathing, increased heart rate, heart murmurs, shortness of braeth, difficulty braething, cough, and excessive sweating. Treatments include diuretics, supplemental oxygen, anti-inflammatories, and sometimes mechanical ventilation.

BRS Graa Allatamy

&4

CLINICAL CORRELATES

Asbastasis is caused by inhalation of asbestos fibers that accumulate and cause irritation and inflammation, leading to dyspnea, cough, chest pains, and over time, an increasing risk of lung ca near, mesatflelioma. Masothalioma is a rare farm of cancer that is caused by chronic inflammation due to asbestos fibers and is found in the mesothelium primarily in the pleura. Its symptoms include shortness of breath due to pleural effusion, chest wall pain, cough, fatigue, and weight loss.

D. Bronchopulmonary segment • Is the anatomic, functional, and surgical unit {subdivision) of the lungs. • Refers to the portion of the lung supplied by each segmental (taltiary) bronchus and its corresponding segmental artery. The pulmonary veins are said ta be intarsegmental. • Each bronchopulmonary segment is surrounded by a delicate connective tissue septum (intersegmental septum). • Is clinically important because the intersegmental pulmonary veins fonn surgical landmarks; thus, a surgeon can remove a bronchopulmonary segment without seriously disrupting the surrounc:Hng lung tissue and major blood vessels.

CLINICAL

Atalectuis is the collapse of a lung by incomplete breath/inhalation, by blockage ofthe air passages, or by very shallow breathing because of anesthesia or prolonged bed rest It is caused by mucus secretions that plug the airway, foreign bodies in the airway, and tumors that compress or obstruct the airway. Signs and symptoms are breathing difficulty, chest pain, and cough.

CORRELATES

CLINICAL

There are many types of lung cancer, including small cell and non-small cell carcinomas, based on histology af the cell type of origin. Small cell carcinoma accounts for 20% and grows aggressively, whereas nolt-9lall cell carcinoma (80%} is divided further into squamous cell carcinoma, adenacarcinoma, and bronchoalvealar large cell carcinoma. Its symptoms include chronic cough, coughing up blood, shortness of breath, chest pain, and weight lass.

CORRELATES

E. Respiratory tract • The conduction portion includes the nasal cavity, nasopharynx, larynx, trachea, bronchi, bronchioles (possess no cartilage), and terminal bronchioles. This portion of the tract serves to warm, humidify, and filter inspired air. • The respiratory portion includes the respiratory bronchlol~ alveolar ducts, atria, and alveolar sacs. Oxygen and carbon dimide gas exchange takes place in this portion across the wall (bloodair barrier) oflung alveoli and pulmonary capillaries.

V. RESPIRATION • Is the vital exchange of oxygen and carbon dioxide that occurs in the lungs. The air-blood barrier consists of alveolar type I cells, basal lamina, and capillary endothelial cells. The alveolar type II cells secrete surfactant

A. Inspiration • Occurs when the intrapleural pressure is decreased by increasing the volume of the pleural space. The diaphragm is the major muscle of quiet inspiration with minor assistance from the

l31IJ.lD1I Thorax

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intercostal muscles (primarily external). The intercostal muscles are important in maintaining a stable intercostal space during respiration. Many muscles are involved during forced inspiration. including the stemocleidomastoid, levator costarum, serratus anterior, scalenes, pectoralis major and minor, and serratus posterior superior muscles. • Quiet inspiration involves the following processes: 1. Contraction of the diaphragm • Pulls the dome inferiorly into the abdomen, thereby increasing tha vertical diamatar of the tb.oralC. 2. Enlargement of the pleural cavities and lungs • Reduc11 the intrapulmonary preaure (creates a negative preaure), thus allowing air to rush into the lungs passively because ofatmospheric pressure.

B. Expiration • Quiet expiration is largely a passive process that occurs when the diaphragm relaxes and the lungs recoil. Involves the following processes:

1. Onrall process Involves relaxation of the diaphragm, the internal intercostal muscles (costal part), and other muscles; decrease in thoracic volume; and increase in the intrathoracic pressure. The abdominal prnsure is dacrnsad, and the ribs are daprnsad. 2. Elastic recoil of the lungs • Occurs because of the elastic fibers in the lung connective tissue and produces a subatmospheric preaure in the pleural cavities. Thus, much of the air is expelled. Forced expiration Requires contraction of the anterior abdominal muscles and the internal intercostal muscles (costal part). •

VI. LYMPHATIC VESSELS OF THE LUNG (see Figure 3.7) Drain the bronchial tree, pulmonary vessels, and connective tissue septa. • Run along bronchioles and bronchi toward the hilum, where they drain to the pulmonary (intrapulmoruuy) and then bronchapulmonaiynodes, which in tum drain to the inferior (carinal) and superior tracheabranchial nodes, the tracheal (paratracheal) nodes, branchamediastinal nodes and trunks, and eventually to the thoracic duct on the left and right lymphatic duct on the right Are not present in the walls of the pulmonary alveoli.

VII. BLOOD VESSELS OF THE LUNG (see Figure 3.8) A. Pulmonaiy trunk • Extends upward from the conus artariosus of the right ventricle of the heart and carries deoxy-

genated blood to the lungs for oxygenation. Is approximately 5 cm long and passes superiorly and posteriorly while crossing anterior to the ascending aorta initially, then to the left of the aorta. It bifurcates into the right and left pulmonary arteries within the concavity of the aortic arch at the level of the sternal angle. Has much lower blood pressure than that in the aorta and is contained within the fibrous pericardium. 1. Left pulmonary artery • Carries deoiygenated blood to the left lung, is shorter and narrower than the right pulmonary artery, and arches over the left primary bronchus. • Is connected to the arch of the aorta by the ligamentum arteriosum, the fibrous remains of the ductus arteriosus.

&6

BRS Graa Allatamy

lnlBrnal jugular vein

01i!:it:ll:J£-:.,,P...-=- - - - Bronchomedlastlnal nodes and trunk

f"~~--~ Tracheal (paratracheaO nodes

Inferior tracheobronchial nodes RGURE 3.7. Tha trachaa, bronchi, and lungs, plus associated lymph nod as.

Left common carotid artery

Pulmonary veins

Apex of heart

RGURE 3.1. Pulmonaiy circulation and circulation through th1 h11rt chamb1rs.

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fi1

Z. Right pulmonary artery •

Runs horizontally toward the hilum of the right lung under the arch of the aorta behind

the ascending aorta and SVC, and anterior to the right bronchus.

CUNICAL

Pulmonary emboli1m Ipulmonary thromboemboli1m) is an obstruction of the pulmonary artery or one of its branches by an embolus (air, blood clot, fat tumor cells, or other foreign materiel!. which arises in the deep veins of the lower limbs or in the pelvic veins or occurs following en operation or after a fracture of a long bone with fatty marrow. Symptoms may be sudden onset of dyspnee, anxiety, and substernal chest pain. Treatments include blood thinners, thrambolytics, which break dawn the clot, and surgical therapy such as pulmonary ambolactomy, which is surgical removal of massive pulmonary emboli.

CORRELATES

B. Pulmonary veins • Axe interngmental in drainage (do not accompany the bronchi or the segmental artery within the pareochyma of the lungs). Terminate as five pulmonary veins, one from each lobe of the luogs. However, the right upper and middle veins commonly join so that only four veins enter the left atrium. Carry oxygenated blood from the respiratory part (alveoli) ofthe lungs and deoxygenated blood from the visceral pleura to the left atrium of the heart. {Gas exchange occurs between the walls of alveoli and pulmonary capillaries, and the newly oxygenated blood enters venulea and then pulmonary veins.)

C. Bronchial arteries • Arise from the thoracic aorta; usually, there is one artery for the rightlung and two for the leftlung. Supply oxygenated blood to the nonr11pir1tory conducting ti11u11 of th1 lung1 and the visceral pleura. .Anastomoses occur between the capillaries of the bronchial and pulmonary systems. D. Bronchial veins • Receive blood from the bronchi and empty into the azygos vein on the right and into the accessory hemiazygos vein or the superior intercostal. vein on the left May receive twigs {small vessels) from the tracheobronchial lymph nodes.

VIII. NERVE SUPPLY TO THE LUNG A. Pulmonary plexus Receives afferent and efferent (parasympathetic preganglionic) fibers from the vagus nerve, joined by branches (sympathetic postganglionic fibers) from the sympathetic trunk and caniiac plexus. Is divided into the anterior pulmonary plaxus, which lies In front of the root of the lung, and the postarior pulmonary plexus, which lies behind the root of the lung. • Has branches that accompany the blood vessels and bronchi into the lung. Sympathetic nerve fibers dilate the lumina of the bronchi and constrict the pulmonaryvessels, whereas parasympathetic fibers constrict the lumina, dilate the pulmonary vessels, and increase

glandular secretion. B. Phrenic nerve • Arises from the third through fifth cervical nerves ( C3-C5) and lies in front ofthe anterior scalene muscle. Enters the thoru by passing deep to the subclavian vein and superficial to the subclaviao arteries. • RWlB anterior to the root of the lung, whereas the vagus nerve runs posterior to the root of thelwig.

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88

• 18 accompanied by the pericardiophrenic branches ofthe Internal thoracic vessels and descends between the mediastinal pleura and the pericardium. • Innervates the Dbrous pericardium, the mediastinal and diaphragmatic pleurae, and the diaphragm for motor and its central tendon for sensory functions.

CLINICAL

Ligation of the phrenic nerve does not always produce paralysis of the corresponding half of the diaphragm beeause the accessory phrenic nerve, derived from the fifth cervical nerve as a branch of the nerve to the subclavius, usually joins the phrenic nerve in the root of the neck or in the upper part of the thorax. Hiccup is an involuntary spasmodic sharp contraction of the diaphragm, accompanied by the approximation of the vocal folds and closure of the glottis of the larynx. It may occur because of stimulation of nerve endings in the digestive tract or the diaphragm. When chronic, it can be stopped with pharmacalogic therapy or by phranic narva ablation.

CORRELATES

IX. DEVELOPMENT OF THE RESPIRATORY SYSTEM A. Development of the trachea and bronchi • Primordium for the lowerrespiratmysystem appears as a larynglllnlch11I groove in theventralftoorof the pharyngealforegut The groove evaglnares to form thelalJllgoln.chaal (ntspiratnry) diffrticulum. • The laryngotracheal dinrticulum is soon separated from the foregut proper by the fonnation ofa tracheaesoph1geal 1eptum. • The tracheo11oph1geal septum divides the foregut Into a ventral portion, the laryngotrachaal tube (primordium ofthe larynx, trachea, bronchi, and lungs), and a dorsal portion (primordium of the oropharynx and esophagus). • Lung buds develop at the distal end of the laryngotracheal diverticulum and branch into the primary, secondary, and tertiary bronchi The tertiary bronchi divide extensively to form bronchiole.!!, terminal bronchioles, and respiratory bronchioles.

B. Derivations or sources • Epithelium and glands in the trachea and bronchi are derived from endoderm, whereas smooth muscles, connective tissue, and cartilage of the trachea and bronchi are derived from visceral (splanchnlc) lateral plate mesoderm. • Visceral pleura is derived from visceral lateral plate mesoderm covering the surface of the lungs, whereas the parietal pleura is derived from somatic lateral plate mesoderm. covering the inside of the bodywall

C. Development of lungs • The lungs undergo five stages of development 1. Embryonic phase (prenatal 2li days ta 6 weksl • The respiratory diverticulum forms as a ventral pouch of the foregut and undergoes preliminary branching.

2. Psaudoglandular phase (prenatal weeks 6-161 •

The conducting (airway) system through the tenninal bronchioles develops. Respiration is not possible.

3. Canalicular ph11e (prenatal weeks 13--251 • Luminal diameter of the conducting system Increases, and respiratory bronchioles, alveolar ducts, and terminal sacs begin to appear. Premature fetuses bom before week 20 rarely survive. 4. Terminal sac plt111 (prenatal wetks 24 ta birth) • MoretermiHI SICI fonn, and alveolartype 1cells and surfactant-producing alveolartype II cells develop. Respiration ls possible, and premature infants can survive with intensive care.

5. Alveolar period (late fetal stage to 8 yean) •

Respiratory bronchioles, tenninal sacs, 11Yeolar ducts, and alveoli increase in number.

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PERICARDIUM AND HEART I. PERICARDIUM • Is a fibroserous sac that encloses the heart and roots of the great vessels and occupies the middl•

m•dialtinum. • Is composed of the fibrous pericardium and serous pericardium. • Receives blood from the perlcardiophrenic, bronchial, and esophageal arteries. Is innervated by sensory fibers from the phrenic nerve and vasomotor fibers from the vagus nerves and the sympathetic trunks.

A. Fibrous paricardium Is a strong, dense, fibrous layer that blends with the adventitia of the roots of the great vessels and the central tendon of the diaphragm.

B. Serous pericardium Consists of the pariatal layer, which lines the hmer surface of the fibrous pericardium, and the visceral lay&r, which forms the outer layer (epicardium) of the heart wall and roots of the great vessels.

CUNICAL

Pericanlitis is an inflammation of the pericardium, which may result in pericardia! effusion, and precordial and epigastric pain, or in advanced cases cardiac tamponade. One may hear a pericardia! murmur or paricardial friction rub (the surfaces of the pericardium become rough, and the resulting friction sounds like the rustle of silk. which can be heard on auscultation). The patient develops dysphagia, dyspnea and cough, inspiratory chest pain, and pulsus paradoxus and, finally, cardiopulmonary collapse.

CORRELATES

C. P1Jicardial cavity • Is a potential space between the visceral layer (epicardium) and the parietal layer of the serous pericardium lining the inner surfaces of the fibrous pericardium.

D. Paricardial 1inu111 1. Transverse sinus Is a subdivision ofthe pericardiaI sac, lying posterior to the ascending aorta and puhnonary trunk, anterior to the SVC, and superior to the left atrium and the pulmonary veins. Is of great hnportmce while performing cardiac surgery. A ligature can be passed through the sinus and tightened around the aorta and pulmonary artery while diverting clrculation through the bypass machine.

2. Oblique sinus Is a subdivision of the p9'icardial sac behind the heart, surrounded by the reflection of the serous pericardium around the right and left pulmonary veins and the inferlorvena cava (IVC).

CUNICAL CORRELATES

Cardiac tamponade is compraaion of the heart caused by accumulation of fluid or blood in the pericardia! cavity from heart wounds or pericardial ..O.ion (passage of fluid from the perica rdial capillaries into the pericardia! sac). It causes compressio11 ofve11aus retum to the heart resulting in decreased diastolic capacity (ventricular filling), reduced cardiac output, increased heart rate, increased venous pressure with jugular vein dimntion, hepatic enlargement, and peripheral edema. Tamponade can be treated with paricardiocentesis. Paricardial atlusion is an accumulation afftuid in tha paricardial space resulting from inflam· mation caused by paricarditis, and tha accumulated fluid compresses the heart, inhibiting cardiac

BRS Graa Allatamy

10

filling (Figure 3.9). It has signs of an enlarged heart a water bottle appea ranee of tile cardiac silhouette, faint heart sounds, and vanished apex beat. It can be treated by pericardiocentesis. Pericardiocent11is is placement of a needle into the pericardiaI cavity for the aspiration of fluid, which is necessary to relieve the pressure of accumulated fluid in the pericardiaI sac. A needle is inserted into the pericardial cavity through the fifth intarcostal space left of tile sternum. Because of the cardiac notch, the needle misses the pleura and lungs, but it penetrates the pericardium.

II. HEART (Figures 3.10 to 3.12) A. General charactarislics • The apex al the heart is the blunt rowided extremity of the heart formed by the left ventricle and lies in the left fifth intercostal space slightly medial to the midclavicular (or nipple) line. This location is useful clinically for determining the left border of the heart and for auscultating the mitral valve.

• Its posterior aspect, called the base, is formed primarily by the left atrium and only partly by the posterior right atrium. • Its right (acute) border is formed by the SVC, right atrium, and IVC, and its left (obtuse) border is formed by the left ventricle. • The heart wall consists of three layers: inner endacardium, middle myocardium, and outer

epicanlium. • The sulcus tarminalis ls a groove on the external surface of the right atrium that marb the function ofthe primitive sinus venosus with the atrium in the embryo and corresponds to a ridge on the internal heart surface, the crista teminalis. • The coronary sulcus, a groove on the external surface of the heart, marks the division between the atria and the ventricles (atrioventricular [AV] groove). The crux is the point at which the lnterventricular and lnteratrial sulcl cross the coronary sulcus. • The cardiovascular silhouatta, or cardiac shadow, is the contour of the heart and great vessels seen on posterior-anterior chest radiographs. Its right border is formed by the SVC, the right atrium, and the IVC. Its left border ls formed bythe aortic arch (which produces the aortic knob), the pulmonary trunk, the left auricle, and the left ventricle. Its inferior border is formed by the right ventricle, and the left atrium shows no border.

B. Internal anatomy of the heart (see Figures 3.12 and 3.13) 1. Right atrium • Has an anteriorly situated rough-walled atrium proper and the awicle lined with pectinate muscles and a posteriorly situated smooth-walled sinus vanarum, into which the two venae cavaeopen. • Is larger than the left atrium but has a thinner wall, and its sinus ven.arum between two venae cavae is separated from the atrium proper by the crista term.lnalis. • The right atrial prassura is normally slightly lower than the left atrial pressure. • Contains the valve (Eustachian) of the IVC and the valve (Thebesian) of the coronary sinus.

l•I

Right auricle Is the conical muscular pouch ofthe upper anterior portion ofthe right atrium, which covers the first part of the right coronary artery.

lbl

Sinus venarum (sinus venarum cavarum) Is a posteriorlysituated, smooth-walled area that is separated from the more muscular atrium proper by the crisla teminalis. Develops from the embryonic sinus venosus and receives the SVC, IVC, coronary sinus, and anterior cardiac veins.

lcl

Pactinata musclas Are prominent ridg11 of atrial myocardium located in the interior of both auricles and the right atriwn.

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fl6URE U. Peric1rdi1l effusion. A: Normii chastx·ray. B: Chastx·rayshowing paricardial effusion in the aame patient. C: CT acan of the cheat with large i:iericardi1I effusion in the darker section around the heert.

C

71

12

BRS Graa Allatamy Aortic arch Brachiocephalic trunk

Right pulmonary artery Right pulmonary

veins~

Right auricle Right coronary artery----

Left ventricle

Apex of heart Posterior lnterventrlcular branch RGURE3.1D. Anterior view of the heart with coronary arteries.

Superior vena cava

Left pulmonary artery Left au rtele

Left ventr1cle

Inferior venacava

Apex of heart

RGURE3.n. Posterior-anterior radiograph af tha th Drax showing the heart and great vessels.

(di Crista tenninalis Is a vertical muscular ridge running anteriorly along the right atrial wall from the opening of the SVC to the opening of the IVC, providing the origin of the pectinate muscl11. • Represents the junction between the primitive 1inu1 venarum (a smooth-walled region) and the right atrium proper and is Indicated externallyby the 1ulc111 tenninali1. lel Venae cordis minima• Are the smallest cardiac veins, which begin in the substance ofthe heart (endocanlium and innermost layer of the myocardium) and end chiefty in the atria at the foramina Ylnarum minimarum cordis.

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Left brachiocephalic

vein Right brachlocephallc

vein

- '"=====:.

Brachiocephalic - trunk

Leftccmmon

===-:...'1-,..._;;;~;;;:::::::~-

carotid artery Left subdavlan

artery

Esophagus

-...___.., .. "~~===--Scapula

Superiorwnacava

-Esophagus

Ttacheabifurealicn Azygosveln

Descending aorta

Ascending aorta..._ Supertor_

venacava

Right pulmonary -

artery

Left pulmonary

artery

Right primary - . bronchus

Right ventricle

Right - - ".=;;::;;;;;:m..,,

pulmonary vein

FIGURE 3.12. Contrast-enhanced computed tomography scan of tile titorax at a aatting titat demonatratu aoft tiaaues.

(f) hlll O'fllis Is an oval-shaped depression in the interatrial septum and represents the site of the foremen ovale, through which blood runs from the right atrium to the left atrium

before birth. The upper rounded margin of the fossa ls called the limb111 fa111 ovale. 2. Left atrium Is smaller and has thicker walls than the right atri'Wll, and its walls are smooth, except for a few pectlnate muscles in 1he auricle.

14

BRS Graa Allatamy

- --- ----1-,........,r----Conus arteriosus ---->rms--T-~---Blcuspld (mttral) valve ~~--Paplllary muscle

Alrtovenb1cular node Alrioventricular bundle

l-\.J---4r--1l'abeculae carneae

Orifice of

coronary sinus lnterventrlcular septum (muscular part)

PurklnJe fibers Septomarginal trabecula

(moderator band) RGURE3.13. Internal anatomy and conducting system of the heart

3.

• Is the molt posterior of the four chambers lying posterior to the right atrium but anterior to the esophagus and shows no structural borders on a posteroanterior radiograph. • Receives oxygenat.ed blood through fourpulmonaryveins. Right ventricle • Makes up the major portion of the ant.erior (stemocostal) surface of the heart. • Contains the following structures: lal Trabeculae carn11e cordis Are anastomosing muscular ridges of myocardium in the ventricles. lb) Papillary mu1cln Are cone-shaped muscles enveloped by endocardium. • Extend from the ant.erior and posterior ventricular walls and the septum. Their apices are attached to the chordae t1ndin11e. Papillary muscles contract to tighten the chordae tendineae, pravanting the cusps or the tricu1pid valva from being 1Y1rted into the atrium by the pressure developed by ventricular contractions. This prevents regurgitation of v1ntricular blood into the right atrium. le) Chordal llndineae Extend from one papillary muscle to more than one cusp of the bicuspid valve. Prevent eversion of the valve cusps into the atrium during ventricular contractions. ldl Conu1 arteriosus (infundibulum) Is the upper smooth-walled portion of the right ventricle, which leads to the pulmonary trunk. 1•1 Septomarginal trabecula (moderator band) • Is an isolat.ed band oftrabeculae carneae that forms a bridge between the inlerventricular (IV) 11ptum and the base of the anterior papillary muscle In the anterior wall of the right ventricle. Is called the moderator band fur its ability to prannt ovardilhlnlian of the ventricle and carries the right limb (Purkinje fibers) of the AV bundle from the septum to the stemocostal wall of the ventricle.

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(t) IV 11ptum

Is the septum that separates the right and left ventricles. Is the place oforigin of the septa! papillary muscle. Is mostly muscular but has a small membranous upper part, which is a common sight ofventricular septa! defects (VSDs). 4. Left ventricle lies at the back of the heart, and its apex is directed downward, forward, and toward the left. Is divided into the left ventricle proper and the aortic vestibule, which is the upper anterior part of the left ventricle that leads into the aorta. Contains two papillary muscles (anterior and posterior) with their chordae tendineae and a meshwork of muscular ridges. thetrabeculae cameat cordis. Performs harder work; has a thicker (two to three times as thick) wall; and is longer, narrower, and more conical shaped than the right ventricle.

CUNICAL

Myocardial infarction is necrosis of the myocardium because of local ischemia resulting from vasospasm or obstruction of the blood supply, most commonly by a thrombus or em bolus in the coronary arteries. Symptoms include a tight squeezing type of chest pain or pressure, congestive heart failure, and mitral valve regurgitation murmur. It can be treated with nitroglycerin (prevents coronary spasm and reduces myocardial oxygen demand), morphine (relieves pain and anxiety), lidocaine (reduces ventricular arrhythmias), or atropine (restores conduction and increases heart rate). Angina pectoris is characterized by attacks of chest pain originating in the heart and felt beneath the sternum, in many cases radiating to the left shoulder, down the left arm, and sometimes to the jaw. It is caused by an insufficient supply of oxygen tD the heart muscle because of coronary artery disease or exertion increasing demand over supply (e.g., exercise, excitement) or emotion (e.g., stress, anger, frustration). Symptoms and treatment are similar to those of myocardial infarction. Prinzmetal angina is a variant form of angina pectoris caused by transient coronary artery spasm. The vasospasm typically occurs at rest, and in many cases, the coronary arteries are normal. Prolonged vasospasm may cause electrocardiogram changes similar to those in myocardia I ischemia, can lead to myocardial infarction, and in rare cases sudden death. Nitroglycerin, nifedipine, amlodipine besylata, and calcium channel blockers can prevent artery spasm. Smoking is the most significant risk factor for the spasm.

CORRELATES

C. Heart valv• (see Figure 3.14) 1. Pulmonaryvalve Lies behind the medial end of the left third costal cartilage and adjoining part of the sternum. Is most audible over the left 11cond intercostal space just lateral to the sternum. Is opened by ventricular systole and shuts slightly after closure of the aortic valve. 2. Aortic valve Lies behind the left haH of the sternum opposite the third intercostal space. Is closed during ventricular diastole; its closure at the beginning ofventricular diastole causes the HCOnd rdub•) hllrt sound. Is most audible over the right Hcond interco118l 1pace just lateral to the sternum. 3. Tricuapid (right AY) valwe lies between the right atrium and the ventricle, behind the right half ofthe sternum opposite the fourth intercostal space, and is covered by endocardium. Is most audible over the right (or left for some people) lower part of the body of the sternum. Has anterior, posterior, and septa! cusps, which are attached by chordae tendineae to three papillary muscles that keep the valve closed against the pressure developed by the pumping action of the heart Is closed during Ylntricular systole (contraction); its closure contributes to the first (•lub•) heart sound.

16

BRS Graa Allatamy

RGURE114.. Positions of the valves of the heart and heart sounds. A. aortic valve; M, mitral valve; P, pulmonary valve; T, tricu1pid valve. Arrows indicate positions of the heart sounds.

4. Bicuspid Ulft AV) valve • Is called the mitral valva because it ls shaped like a bishop's miter. • Lies between the left atrium and the ventricle, behind the lefthalfofthe sternum at the fourth costal cartilage, and has two cusps: a l&Iger anterior and a smaller posterior.

• Closas slightly befara the bicuspid valve during ventricular contraction (systole); ill closure at the onset ofventricular systole causes the first (•lub•) hean sound. • Is most audible over the apical region of the heart in the left fifth inlarcostal space al Iha midclavicular line.

CLINICAL CORRELATES

Mitral valve prolapse is a condition in which the valve collapses into the left atrium and thus fails to close properly when the left ventricle contracts. It may produce chest pain, shortness of breath, palpitations, and cardiac arrhythmia. In most cases, no treaunent is needed. Endocanlitis is an infection of the endocardium of the heart. most commonly involving the heart valves and is caused by formation of bacterial colonies on the valves. Symptoms include fatigue, weakness, fever, night sweats, anorexia, heart murmur, and shortness of breath. Risk factors include a damaged abnormal heart valve, mitral valve prolapse, and certain congenital heart defects. Cardiac murmur is a characteristic sound generated by turbulence of blood flow over a compromised valve of the heart.

D. Heart sounds 1. First (•lub•) saund • Is caused by the closure of the bicuspid and mitral valves at the onset of ventricular systole. Z. Saeond (•dub•) sound • Is caused by the closure of the aortic and pulmonary valves (and vibration of the walls ofthe heart and major vessels) at the onset of ventricular diastole.

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E. Conducting system of tltt heart (see Figure 3.13) Is composed orspecialized cardiac muscle cells that lie immediately beneath the endocardium and carry impulses throughout the cardiac muscle, signaling the heart chambers to contract in

the proper sequence. 1. Sinoatrial node ls a small mass of specialized cardiac muscle fibers th.at lies in the myocardium at the upper end af the crista 1:8nninalis near the opening of the SVC in 1he right atrium. ls known as the pacemaker of the heart and initiates the heartbeat, which can be altered by autonomic nervous stimulation (sympathetic stimulation speeds it up, and vagal stimulation slows it down). Impulses spread in a wave along the cardiac muscle fibers of the atria and also travel along an intemodal pathway to the AV node. ls supplied by the sinus node artery, which is a branch of the right coronary artery. 2. AYnodt Iles In the sepbtl wall or the right atrium, superior and medial to the opening of the coronary sinus, receive& the Impulse from the sinoatrlal (SA) node, and passes It to the AVbWldle. ls supplied by the AV nodal artery, which usually arises from the right coronary artery opposite the origin of the posterior interventricular artery. ls innervated by autonom.lc nerve fibers. although the cardiac muscle fibers lack motor endings. 3. AV bundle (bundle af His) Begins at the AV node and runs along the membranous part ofthe interventricular septum. Splits into right and left branches, which descend into the muscular part ofthe interventricular septum, and breaks up into terminal conductingfibers (Purlcinje fiben) to spread out into 1he ventricular walls.

CUNICAL CORRELATES

Damage to the conducting IJlflm can cause heart block, which interferes with the ability of the ventricles to receive the atrial electrical impulses. A delay or disruption of the electrical signals produces an irregular and slower heartbeat, reducing the heart's efficiency in maintaining adequate circulation. Heart block requires a pacemaker to be implanted. Atrial or ventricular fibrillation is a cardiac arrhythmia resulting from rapid irregular uncoordinated contractions of the atrial or ventricular muscle beca use of fast repetitive excitation of myoca rdial fibers, causing palpitations, shortness of breath, angina, fatigue, congestive haart failure, and sudden cardiac death.

F. Coronary arteries (see Figure 3.10) Arise from the ascending aorta. Have maximal blood flow during diastole and minimal blood flow during systole because of compression of the arterial branches in the myocardium during systole. 1. Right coronary artery Arlse&from the anterior (right) aortic sinus of the ascending aorta,. runs between the root of the pulmonary trunk and the right auricle, and then descends in the right coronary sulcus, and generally supplies the right atrium and ventricle. Gives rise to the following: (a) SA nodal artery Passes between the right atrium and the root of the ascending aorta, encircles the base of the SVC, and supplies the SA node and the right atrium. (b) Marginal artery Runs along the inferior border toward 1he apex and supplies the inf'erior margin of the right ventricle. (c) Posterior IV (pol11rior descending) artery In a right dominant coronary artery, it Is a larger terminal branch and supplies part of the IV septum, left ventricle, and the AV node. Coronary artery dominance Is determined by which coronary artery gives rise to the posterior lnterventricular artery. Right coronarydominance Is more common than left coronarydominance.

18

IRS Gross Anatomy (d) AV nodal artary Arises opposite the origin of the posterior IV artery and supplles the AV node.

CUNICAL CORRELATES

Coronarr atheroaclero1i1 is characterized by deposition of sclerotic plaques containing cholesterol, lipid material, or fibrin clot onto the internaI surface of blood vessels. Plaques impair myocardial blood flow by narrowing the vessel lumen, leading to isch· emia and myocardial infarction. Coronaiy angioplasty is an angiographic reconstruction (radiographic view of vessels after the injection of a radiopaque material) of a blood vessel made by enlarging a narrowed coronary arterial lumen. It is parfonned by peripheral introduction of a balloon-tip cathater and dilation of the lumen. A metal stent is often placed if the lumen does not remain open after initial angioplasty.

CUNICAL CORRELATES

Coronarr bypa11 or coronary artary bypass graft (CABG) is a surgical procedure that restores blood flow to the heart muscle by rerouting blood flow around narrowed or occluded coronary arteries. It involves grafting a section of healthy vessel (taken from another location) both proximal and distal to the area of occlusion, "bypassing .. the obstruction.

2. Lift coronary arterr Arises &om the left aortic sinus ofthe ascending aorta, just above the aortic stmilunar valve. Is shorter than the right coronaryartery and is usually distributed to more ofthe myocardium. Gives rise to the following: (a) Anterior IV (left anterior descending) artary Generally supplies anterior aspects of the right and left ventricles and is the chler source of blood to the IV septwn and the apex:. (b) Circumflex artery Rnns in the coronary sulcus, gives off the left marginal artery, supplies the left atrium and (posterior) left ventricle, and anastomoses with the terminal branch of the right coronary artery. G. Cardiac veins and coronary sinus (see Figure 3.15) 1. Coronarysinus Is the largest vein draining the heart and lies in the coronary aulcus, which separates the atria &om the ventricles. Opens into the right atrium between the opening of the IVC and the AV opening. Has a one·cusp valve at the right margin or its aperture. Recelves the great, middle, and small cardiac velwl; the oblique vein of the left atrium; and the posterior vein of the left ventricle. 2. Great cardiac vein Begins at the apex ofthe heart and ascends along with the IV branch of the left coronary artery. Turns to the left to lie in the coronary sulcus and continues as the coronary ainut. 3. Middle cardiac wein Begins at the apex: of the heart and ascends in the posterior IV groove, accompanying the posterior IV branch or the right coronary artery. Drains into the right end of the coronary sinus. 4. Small cardiac vein Runs along the right margin of the heart In company with the marginal artery and then posteriorly in the coronary sulcus to end in the right end of the coronary sinus. 5. Oblique vain of Iha left atrium Descends to empty into the coronary sinus, near its left end.

l3:JitiCill Thorax

19

Right pulmonary artery Righi pulmonary wins __.!~~...

Middle cardiac vein RGURE3.15. Antllrior view of the hHrt.

&. Anterior cardiac vein • Drains the anterior right ventricle, crosses the coronary groove, and ends directly in the right atrlwn. 1. Smallest cardiac veins lvenaa cordis minimaa) • Begin in the wall of the heart and empty directly into its chambers.

H. Lymphatic vassals of 1ha heart • Receive lymph from the myocardium and epicardium. • Follow the rightcoronaryarteryto emptylnto the anterior madiallinal nodes and follow the left coronary artery to empty into a tracheobronchial node.

I. Cardiac plexus • Receives the superior, middle, and inferior cervical and thoracic cardiac nerves from the sym· pathetic trunks and the vagus nerves. • Is divisible into the superficial cardiac plexus, which lies beneath the arch of the aorta in front of the pulmonary artery, and the d11p cardiac plexus, which lies posterior to the arch of the aorta in front of the bifurcation of the trachea. • Richly innervates the conducting system ofthe heart: the right sympathetic and parasympathetic branches terminate chieflyin the region of the SA node, and the left branches end chiefly in the region of the AV node. The cardiac muscle fibers are devoid of motor endings and are activated by the conducting system. • Supplies the heart with sympathetic fibers, which incra111 the rate and force of the heartbeat and cause dilation of the coronary arteries, and parasympathetic fibers, which decrease the heart rm and constrict the coronary arteries.

Ill. GHEAT VESSELS A. Ascending aorta • Takes its origin from the left'Y1!Iltricle within the pericardial sac and ascends behind the stemum to end at the level of the sternal angle. • Lies in the middle madiallinum, has three aortic sinuses located immediately above the cusps of the aortic valve, and gives rise to the right and left coronary arteries.

BRS Graa Allatamy

Ill

B. Arch DI the aorta • Is found within the superior mediastinum, begins as a continuation of the ascending aorta, and archu ner the right pulmonary artery and the left main bronchus. • Forms a prominence that is visible on the radiograph as the aortic knob. • Gives rise to the brachiocephalic, left common carotid, and left subclavian arteries.

CLINICAL CORRELATES

Aneurysm DI the aortic arch is a sac formed by dilation of the aortic arch. When it occurs in the descending aortic arch, it can compress the left recurrent la ryngaa I nerve, leading ta coughing, hoarseness by paralysis of the ipsilateral vocal card. It may cause dysphagia (difficulty in swallowing), resulting from pressure on the esophagus, and dyspn11 (difficulty in breathing), resulting from pressure on the trachea, root of the lung, or phrenic nerve.

CLINICAL CORRELATES

Marten syndrome is an inheritable disorder of connective tissue that affects the skeleton (causing long limbs}, eyes (dislocated lens), lungs (pneumothoraxJ, and heart end blood vassals (aortic root dilation, aortic aneurysm, aortic regurgitation, and mitral valve prolapse). It may be treated with medications that red uca aortic root dilation.

C. Superior vena can Is formed by the wtlon of the right and left bra.chlocephalic veins and retmn111 blood from all structures superior to the diaphragm, except the lungs and heart. • Descends on the right side of the ascending aorta, receives the azygos vein, and enters the right atrium. Its upper halfis in the 1upariarmadiallinum, and its lower half ls in the middi a madiastinum. •

D. Pulmonary trunk • Arises from the conus arteriosus of the right ventricle, passes obliquely upward and backward across the originand left side of the ascending aorta within the fibrous pericardium, and bifurcates into the right and left pulmonary arteries in the concavity ofthe aortic arch.

IV. DEVELOPMENT OF THE HEART (see Figure 3.16) • Begins as angi.ogenic cell clusrers formed in the splanchnic lateral plate mesodenn. • Involves fusion of two endocarcliel tubes into a single primitive hurt tube.

A. PrimitiYI heart tube • It is formed by fusion of two endocardiel heart tubes of 111planchnic mesodenn origin in the

cardiogenic region of the embryo. • It develops into the endocardium, and the 111planclmic me111oderm surrounding the tube develops into the myocardium and epicardium. • It fonns five dilations, including the truncus arteriosus, bulbus cordis, primitive ventricle, primitive atrium, and sinus venosus. • It undergoes folding into a U-shape, bringing the arterial and venous ends of the heart together, moving the ventricle caudally and the atriwn cranially.

B. Fata of five dilations of the primitive heart tube • Truncus arteriosus {ventral aorta) forms aorta and pulmonary trunk. • Bulbus cordis forms conus cordis or conus arteriosus {smooth partofright ventricle) and aortic vestibule (smooth part of left ventricle at the root of the aorta).

• Primitive ventricle forms trabeculated part of right and left ventricles.

liJtru!lll Thorax

'X

11

/Pertcardlum

I

Pericardia!

Truncus artertosus ' Bulboventricular ) sulcus

cavity

\ I I

Bulbus cordis

I Sinus wnosus

Sinus

venosus

Ventricle

Prtmlllve

Truncus arterlosus

right

abium

----Prtmlllve left abium

--++-Primitive left ventricle

Trabeculated part of right ventricle FIGURE 3.11. Formation oftha cardiac loop and haart A-C: Cardiac loop. D and E: Haart (Raprinted with parmission from Langman J. Medical Embryology. 4th ad. Baltimore, MD: Williams&. Wilkins; 1981:162.J

• Primitive atrium forms trabeculated part of right and left atria. • Sinus wanosus forms sinus ven•rum (smooth part of right atrium), coronary sinus, and oblique vein or the left atrium.

C. Division of the hean into four chambers • Heart divides into its four chambers by formation of its septa and valves. • Four main septa involved in dividing the heart include the aorticopulmonary (AP) septum, the atrial septum, the AV septum, and the N septum.

1. Paltition of the truncus arllriosus and bulbus cordis • The truncal ridg11 and the bulbar ridg11 derived from neural crest mesenchym.e growin a spiral fashion and fuse to form the AP septum. • The AP 11ptum divides the truncus arterlosus into the aorta and pulmonary trunk. Z. Partition oftha primitive atrium •

Septum primum grows toward the AV endocardial cushions from the roof of the primitive atrium.

• •

Septum secundum forms to the right of the septum primum and fuses with the septum primum to form the atrial uptum, which separates the right and left atria. Foramen primum forms between the free edge of the septum.prim.um and the AV 11ptum, allowing a passage between the right and left atria. The foramen is closed by growth of the septum primum.

• •

Foraman sacundum forms in the center of the septum prlmum. Foremen oval1 is an oval opening In the septum secundum that provides a communication between the atria. See Fetal Circulation.: VIl.A.1.

IRS Gross Anatomy

12.

3. Partition of the AY canal The dorsal and ventral endocardlal cushions fuse to form the AV septum. The AV septum partitions the AV canal Into the right and left AV canals. 4. Partition of the primitive ventricle Muscular IV septum develops as an outgrowth of the muscular wall in the floor of the primitive ventricle and grows towanl the AV septum but stops to create the N foramen, leaving the septum incomplete. Membranous IV Hpblm forms by fusion ofthe bulbar ridges with the endocardial cushion, the AP septum, and the muscular part of the N septum. The membranous N septum closes the N foramen, completing partition of the ventricles.

CUNICAL

Tetralogy of Fallot occurs when the AP septum fails to align properly with the AV septum, resulting in (1) pulmon11y stenosis (obstruction to right ventricular outflow), (2) VSD, (3) overriding aorta {dextroposition of aorta), and {4) right ventricular hypertrophy (Figure 3.17). It is characterized by right-to-left shunting of blood and cyan11i1. Overriding aorta {dextroposition of aorta) is when the aorta (its outlet) overlies both ventricles (instead of over the left ventricle), directly above the VSD, causing the aorta to arise from both ventricles. TraMposition ofthe greatventls occurs when the AP septum fails to develop in a spiralfash· ion, causing the aorta to arise from the right ventricle and the pulmonary1runk to arise from the left ventricle. It results in right-to-left shunting of blood and cyanosis. Thus, the 1ransposition must be accompanied by a VSD or a patent ductus artariosus for the infant to survive after birth•

CORRELATES

•

Oxygenated blood

D Deoxygenated blood D Mixed blood Pulmonary valve

sten081•

Right ventricle outflow tract

narrowing

Ventricular septal defect (VSD)

Right ventricle FIGURU..11. Tstralogy of Fallat

Right ventricle hypem>phy

l31IJ.lD1I Thorax

83

CUNICAL CORRELATES

Atrial septaI defect (ASD) is a congenita I defect in the septum between the atria due to failure of the foramen primum or 11cundum to clOll normally, resulting in a patent foraman ovale. This congenital heart defect shunts blood from the left atrium to the right atrium and ca uses hypertrophy of the right atrium, right ventricle, and pulmonary trunk. and thus mixing of oxygenated and deoxygenated blood, producing cyanosis. Symptoms of the defect are dyspnea, shortness of breath, and palpitations, and its signs include abnormal heart sounds, murmur, and heart failure. It can be treated by surgical closure of the defect or a procedure without surgery, which introduces a catheter through the femoral vein and advances it into the heart, where the closure device is placed across the ASD and the defect is closed. If not repaired, a blood clot, which usually forms in the deep veins of the thigh or the leg, can travel to the right atrium, the left atrium through the ASD, the left ventricle, the systemic circulation, and eventually mthe brain, causing

a stroke.

CUNICAL CORRELATES

VSD occurs commonly in the membranous part of the IV septum because of the failure of the membranous IV septum to develop, resulting in left-to-right shunting of blood through the IV foramen, which increases blood flow to the lungs and causes pulmonary hypertension. Symptoms of the defect are shortness of breath, fast heart rate and breathing, sweating, and pallor, and its signs include a loud, continuous murmur and congestive heart failure.

V. DEVELOPMENT OF THE ARTERIAL SYSTEM A. Formation • The arterial system develops from the aortic arches and branches of the dorsal aorta. B. Aortic arch derivativn • Aortic arch 1 regresses as the later arches form. A small portion contributes to the formation of the maxillary artery. Aortic arch 2 regresses as the later arches form. Arch 2 contributes to the formation of the byoid and stapedial arteries. Aortic arch 3 forms the common carotid arteries and the prmimal part of the internal carotid arteries. • Aortic arch 4 forms the aortic arch, the brachiacaphalic artery, and the prox1mal subclavian artery on the right. Aortic arch 5 has no derivative. • Aortic arch 6 forms the proximal pulmonary arteries and ductus arteriosus. C. Dorsal aorta 1. Posterolateral branches • Form the intercostal, lumbar, vertebral, cervical, internal thoracic, and epigastric arteries and arteries to the upper and lower limbs. 2. Llter1I branches Form the renal, suprarenal. and gonadal arteries. 3. Ventral branches • Vitelline arteries form the celiac (foregut), superior mesenteric (midgut), and inferior mesenteric (hindgut) arteries. Umbilical arteries form a part of the internal iliac and superior vesical arteries.

BRS Graa Allatamy

84

VI. DEVELOPMENT OF THE VENOUS SYSTEM • The venous system develops from the vitelline, umbilical, and cardinal veins, which drain into the sinus venoaus.

A. Vitalline veins • Return poorly oxygenated blood from the yolk sac. • Right vein forms the hepatic veins and sinusoids, ductus venosus. hepatic portal, superior mesenteric, inferior mesenteric, and splenic veins and part of the IVC. • Left vein forms the hepatic veins and sinusoids and ductus venosus.

B. Umbilical veins • Carry well-oxygenated blood from the placenta. • Right vein degenerates during early development. • Left vein connects to the ductus venosus and after birth fonns the llgamentu.m teres hepatis. C. Cardinal veins • Return poorly oxygenated blood from the body of the embryo. • Anterior cardinal vein forms the internal jugular veins and SVC. • Posterior cardinal vein forms a part of the NC and common iliac veins. • Subcardinal vein forms a part of the IVC, renal veins, and gonadal veins. • Supracardinal vein forms a part of the IVC, inten:ostal, azygos, and hemiazygos veins.

VII. FETAL CIRCULATION (see Figure 3.18) A. Thi ...... • Has blood that is oxygenated in the placenta rather than in the lungs. • Has three shunts that partially bypass the lungs and~

1. For1men DY11l1

• • •

Is an opening in the septum secundum. Usually closes functiooally at birth, with anatomic closure occurring later. Shunts blood from the right atrium to the left atrium, partially bypassing the lungs (pulmonary circulation).

2. Ductu1 arteriosus • • • •

Is derived from the sbtth. aortic arch and connects the bifurcation ofthe pulmonary trunk with the aorta. Closes functionally soon after birth, with anatomic closure requiring several weeks. Becomes the llgamentum arteriosum, which connects the left pulmonary artery (at its origin from the pulmonary trunk) to the concavity of the arch of the aorta. Shunts blood from the pulmonary trunk to the aorta, partially bypassing the lungs (pulmonary circulation).

CLINICAL CORRELATES

Patent ductus 1rt1riosu1 results from failure of the ductus arteriosus to close after birth, and it is common in premature infants. The ductus art1rios111 takes origin from the left sixth arch.

3. Ductus vanosus • •

Shunts oxygenated blood from the left umbilical vein (returning from the placenta) to the IVC, partially bypassing the liver (portal circulation). Joins the left branch of the portal vein to the IVC and is obliterated to become the llgamentwn venosum after birth.

l3:JitiCill Thorax

85

Internal jugular win

Lung ~111'1'1:----+-Pulmonary vein

Umbilical vein Umblllcal artery

Placenta RGURE3.1B. Fatal circulation.

B. Umbilical artarias • Carry blood to the placenta for reoxygenation prior to birth. • Become medial umbilical ligaments after birth, after their distal parts have atrophied.

C. Umbilical veins • Carry highly oxygenated blood from the placenta to the fetus. • Consist of the right vein, which is obliterated during the embryonic period, and the left vein, which is obliterated to form the ligamentum teres hepatis after birth.

STRUCTURES IN THE POSTERIOR MEDIASTINUM

I. ESOPHAGUS Is a muscular tube (approximately 10 in. long) that extends from the pharynx to the stomach, descending behind the trachea. • Has three constrictions: (1) upper or pharyngoesophageal constriction at the beginning of the esophagus at the level ofthe cricoid cartilage (C6) is caused by the cricopharyngeus muscle (upper esophageal sphincter); (2) middle or thoracic constriction where it is crossed bythe aortic arch and then left main bronchus; and (3) inferior or diaphragmatic constriction at the esophageal hiatus of the diaphragm (TIO). The left atrium also presses against the anterior surface of the esophagus. • Has a physiologic sphincter, which is the circular layer of smooth muscle at the gastroesophageal junction. This is called the inferior nophagaal sphinclarbycliniclans. • Receives blood from the inferior thyroid artery in the neck and branches of the aorta (bronchial and esophageal arteries) and from the left galbic and left inferior phrenic arteries in the thorax.

86

IRS Gross Anatomy

CUNICAL CORRELATES

Achalasia of the esophagus is a condition of impaired 11ophagaal contractians because of a failure of the inferior naphagaal sphincter to relax, as a result of degeneration of the myenteric (Auerbach) plexus in the esophagus. It causes an obstruction to the passage of food in the terminal esophagus and exhibits symptoms of dysphagia for solids and liquids, weight loss, chest pain, nocturnal cough, and recurrent bronchitis or pneumonia. Systemic 1cl1rosi1 (sclerod1rm1) is a systemic collagen vascular disease and has clinical features of dysphagia for solids and liquids, severe heartburn, and 110ph1111l llricture.

II. BLOOD VESSELS AND LYMPHATIC VESSELS (see Figures 3.19 and 3.20) A. Thoracic aorta Begins at the level of the fourth thoracic vertebra. Descends on the left side of the vertebral column and then approaches the median plane to end in front of the vertebral colunm. by passing through the aortic hiatus of the diaphragm. Gives rise to nine pairs of posterior int1rcostal arteries and one pair of 1ubcostal 1rteri11. The first two intercostal arteries arise from the highest intercostal arteries of the costocervical trunk. The posterior intercostal artery gives rise to a collateral branch, which runs along the upper border of the rib below the space. Also gives rise to pericardiaL bronchial (one right and two left), esophageal, mediastinal, and superior phrenic branches.

CUNICAL CORRELATES

Coarctation of the aorta (Figure 3.19) occurs when the aorta is abnormally constricted just inferior to the ductus arteriosus, in which case an adequate collateral circulation develops before birth. It causes (a) a characteristic rib notching and a high risk of cerebral hemorrhage; (b) tortuous and enlarged blood vessels, especially the internal thoracic, intercostal, epigastric, and scapular arteries; (c) an elevated blood pressure in the radial artery and decreased pressure in the femoral artery; and (d) the femoral pulse to occur after the radial pulse (normally, the femoral pulse occurs slightly before the radial pulse). It leads to the development of important collateral circulation over the thorax. which occurs betw11n the (a) anterior intercostal branches of the internal thoracic artery and the posterior intarcostel arteries; (b) superior 1piga11ric branch of the int1rnal thoracic artery and the inferior apigastric artery; (c) superior intercostal branch of the costocervical trunk end the third pDSterior intercostal artery; and (d) posterior intercostal arteries and the descending scapular (or dorsal scapular) artery, which anastomoses with the suprascapular and circumflex scapular arteries around the scapula.

B. Azygos venous system (see Figure 3.20) 1. Azygos [unpaired)vein Is formed by the union of the right ascending lumbar and right subcostal veins. Its lower end is connected to the IVC. Enters the thorax through the aortic opening of the diaphragm. Receives the right intercostal veins, the right superior intercoltal vein, and the hemiazygos and accessory hemiazygos veins. Arches overtltt root of lht right lung and empties into lht SVC, ofwhich it is the first tributary.

2. Hemiazygos vain Is formed by the union of the left subcostal and ascending lumbar veinB. lts lower end is connected to the left renal vein. Ascends on the left side of the vertebral bodies behind the thoracic aorta, receiving the 9th, 10th, and 11th posterior intercostal veins.

l:3:dJtitiill Thorax

87

Thyrocervlcal trunk Posterior lntercostal artery

Aortk: arch

Deep branch of transverse cervlcal artery Suprascapular artery

subclavlan artery

Superior intercostal artery Clrcumflax scapular artery Thoracodorsal artery

Musculophrenlc artery Superior epigastric artery

RGURE3.19. Coarctation afthe aorta.

3. Accessory hamiazygos nin • Begins at the fourth or fifth lntercostal space; descends, receiving the fourth or fifth to eighth intercostal veins; turns to the right; passes behind the aorta; and terminates in the azygos vein.

4. Superior intercostll vein • Is formed by a union of the second, third, and fourth posterior intercostal veins and drains into the azygos vein on the right and the brachiocephalic vein on the left.

5. Posterior intercostal veins • The first intercostal vein on each side drains into the corresponding brachiocephalic vein. • The second, third, and often the fourth intercostal veins join to form the superior intercoatal vein. • The rest of the veins drain into the azygos vein on the right and into the hemiazygos or ac-

cessory hemiazygos veins on the left. C. Lymphatics 1. Thoracic duct (see Figures 3.20 and 3.21) • Begins in the abdomen at the cistema chyli, which is the dilated junction of the intestl.nal, lumbar, and descending intercostal trunks. • Is usually beaded because of its numerous valves and often forms double or triple ducts. Drains the lower limbs, pelvis, abdomen, left thorax, left upper limb, and left side ofthe head and neck. • Passes through the aortic opening of the diaphragm and ascends through the posterior mediastinum between the aorta and the azygos vein. • Arches laterally over the apex of the left pleura and between the left carotid sheath in front and the vertebral artery behind, runs behind the left internal jugular vein, and then usually empties into the junction of the left internal jugular and subclavian veins.

2. Right lymphatic duct • Drains the right sides of the thorax, upper limb, head, and neclc. Much of the left lower lung lobe drains to the rightlymphatic duct. • Empties into the junction of the right internal jugular and subclavian veins.

Brachiocephalic veins Internal jugular vein

---=='="'- - - First intercostal vein

1+--

-i.i:= =----Left superior lnterco61al vein

1'1--------Aocessory hemiazygos vein

Ascending lumber v e i n - - - - --+1

FIGURE 120. Azygos venous systam.

RGURE 3.11. All areas except the shaded area (upper right quadrant) are drained by the thoracic duct

•

liJtru!lll Thorax

19

Ill. AUTONOMIC NERVOUS SYSTEM IN THE THORAX (Figure 3.22) Is composed of motor, or efferent, nerves through which cardiac muscle, 1mooth muscle, and gland1 are innervated. • Involves two neurons: preganglionic and poatganglionic. It may include visceral afferent IVAUib111 because they nm along with visceral afferent IVE) fibars. Consists ofsympathetic (or thoracolumbar outflow) and parasympathetic (or cranJosacral outflow)

systems. • Consists of cholinergic fibers (sympathetic preganglionic, parasympathetic preganglionic, and postganglionic), which use acetylcholine as the neurotransmitter, and adranargic fibers (sympathetic postgangllonic), which use norepinephrine as the neurotransmitter (except those to sweat glands [chollnerglc]).

A. Sympathetic nervoua ayatem Is a catabalic (anargy-cansuming) system that mobilizes energy stores for increased activity. It is often referred to as the fight-ar-flight division, but ls always involved in regulating normal resting functions (such as normal vascular tone). • Contains pregangliooic cell bodies that are located in the lateral horn (intermediolateral cell column} of the spinal cord segments between Tl and L2.

Greater splanchnlc nerve---:=----Hc~..,,,_--,. Lesser aplanchnlc nerve----,.---....

i'"'"1~-..;~

L.eest splanchnic nerw Superior mesenteric ganglion (aorticorenal)------H......::::--- - - - -n1 Lumbar splanchnic nerve-----1-.P~~~

Pelvic splanchnlc nerve

\ RGURE 122. Autonomic nervous system.

90

IRS Gross Anatomy Has preganglionic fibers that pass through the white rami communicantes and enter the sympathetic chain ganglion, where they synapse. Has postgangtionic fibers that join each spinal nerve byway of the grayrami communicantes and supply the blood vessels, hair follicles (arrector pill muscles), and sweat glands. Increases the heart rate and dilates the coronary artarias and the bronchial lumen. 1. Sympatltelic trunk Is composed primarily ofascending and descending preganglionic sympathetic fibers and VA fibers and contains the cell bodies of the postganglionlc sympathetic (VB) fibers. Descends in front of the neck: of the ribs and the posterior !ntercostal vessels. Contains the cervicothoracic (or stellate) ganglion, which is funned by fusion of the inferior cervical ganglion with the first thoracic ganglion. Enters the abdomen through the crus ofthe diaphragm or behind the medial lumbocostal arch. Gives rise to cardiac, pulmonary, mediastinal, and thoracic splanc:hnic branches. Is connected to the thoracic spinal nerves by gray and white rami c:ommunic:antes.

CUNICAL

S1ellate black is an injection of local anesthetic naa r the stellate ganglion by placing the tip of the needle near the neck of the first rib. It produces a temporary interruption of sympathetic function such as in a patient with excess vasoconstriction in the upper limb.

CORRELATES

2. Rami communicantes (1) White rami communicantas Contain preganglionic sympathetic VE (myelinated) fibers with call bodias located In the lateral ham (intermedlolateral cell column) of the spinal cord and VA fibers with call bodi11 located in the dorsal root ganglia. Are connected to spinal nerves Tl through L2. (b) Gray rami communicantes Contain postganglionic sympathetic VE (unmyelinated) fibers that supply the blood vessels, sweat glands, and arrector pill muscles of hair follicles. Axe connected to every spinal nerve and contain fibers from cell bodi11 that are located in the sympathetic trunk. 3. Thoracic splanchnic nerw11 Contain sympathetic preganglionic VE fibers &om cell bodies located in the lateral horn of the spinal cord and YA fibers with cell bodies located in the dorsal root ganglia. Thoracic splanchnic nerves pass through the diaphragm to supply sympathedc innervadon to abdominal organs. They synapse with postgangllonic cell bodles located In ganglia and plexuses associated with major arteries (celiac ganglion, superior mesenteric ganglion, aorticorenalganglion, renal plex:us}. .Although these are described as distinct ganglia, they are in reality heavily interconnected and dUDcultto classify with speclflcity. (a) Greater splanchnic nesve Arises &om the fifth through ninth thoracl.c sympathedc ganglia, perforates the crus of the diaphragm, or occasionally passes through the aortic hiatus, and ends in the celiac ganglion. Some fibers continue past the celiac ganglion into the superior mesenteric ganglion. (b) Lts1er splanchnic nerve Is derived &om the 10th and 11th thoracic: ganglia, pierces the crus of the diaphragm, and ends In the aomcorenal ganglion. Some fibers connect to the superior mesenterlc ganglion. (c) Least splanchnic narn 18 derived from the 12th thoracic ganglion, pierces the crus ofthe diaphragm, and ends in the ganglia of the renal plexus.

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B. Parasympathetic nervous splam • Isa homeostatic oranabolic lanergy-connrving) system, promoting quiet and orderly processes of the body. • Is not as widely distributed over the entire body as sympathetic fibers; the body wall and extremities have no parasympathetic nerve supply. Has preganglionic fibers nmning in cranial nerves (CNs) Ill, VII, and IX that pass to cranial autonomic ganglia (i.e., the ciliary, submandibular, pterygopalatine, and otic ganglia), where they synapse with postganglionic neurons. Has parasympathetic fibers in the ¥111111 n11YB (CN X) that supply all ofthe thoracic and abdominal viscera, except the descending and sigmoid colons and other pelvic viscera. These structures a.re innervated by the pa Ivie splanchnic narv11 (S2-S4). The vagus nerve contains the parasympathetic preganglionlc fibers with cell bodies located in the medulla oblongata and the visceral afferent (VA) fibers with cell bodies located in the inferior (nodose) ganglion. • Dacreans tfla haart rata, constricts bronchial lumen, and causes vnoconstriction of the coronary arteries. 1. Right vagus nerve • Gives rise to the right recurrent laryngeal nerve, which hooks around the right subclman artery and ascends into the neck between the trachea and the esophagus. • Crosses anterior to the right subclavian artery, runs posterior to the SVC, and descends at the right surlace of the trachea and then posterior to the right main bronchus. • Contributes to the cardiac, pulmonary, and esophageal plexuses. • Forms the posteriorvagal trunk (or gastric nerves) at the lower part ofthe esophagus and enters the abdomen through the esophageal hiatus. 2. I.aft vagus nerve • Enters the thorax between the left common carotid and subclavian arteries and behind the left brachiocephallc vein and descends on the arch of the aorta. • Gives rise to the left recurrent latyngaal nerve, which hooks around the arch of the aorta to the left of the ligamentum arteriosum. It ascends through the superior mediastinum and the neck in a groove between the trachea and the esophagus. • Gives off the thoracic cardiac branches, breaks up into the pulmonaryplemses, continues into the esophageal pl.ems, and then forms the anterior vagal trunk.

CUNICAL

Injury to the recurrent laryngeal nerve may be ca used by a bronchogenic or esophageal carcinoma, enlargement of mediastinal lymph nodes, an aneurysm of the aortic arch, or thyroid and parathyroid surgeries, causing respiratory obstruction, hoarseness, and an inability to speak because of paralysis of the vocal cord. Vagotomy is transaction of the vagus nerves at the lower portion of the esophagus in an attempt to reduce gastric secretion in the treatment of peptic ulcer.

CORRElATES

C. Organ-specific effects of autonomic actiwity Sympathetic stimulation increases heartmte, dilates coronary arteries, and thus increases blood :tlowthroughthe vessels, supplying more oxygen and nutrients to the myocardiwu. Sympathetic nerves also produce bronchodilation and vasoconstriction of pulmonary vessels. Parasympathetic stimulation slows the heart rate; constricts the coronary arteries; produces bronchoconstriction (motor to smooth muscle), vasodilation of the pulmonary vessels; and increases glandular secretion of the bronchial tree (secretomotor).

HIGH-YIELD TOPICS The sternum can be used for bone marrow biopsy because ofits accessible location and its posse.gsum of hematopoietlc marrow throughout life.

92

BRS Gross Anatomy The sternal angle (of Louis) is the junction between the manubrium and the body of the sternum located at the level where (1) the second ribs articulate with the sternum, (2) the aortic arch begins and ends, (3) the trachea bifurcates into the right and left primary bronchi, and (4) it marks the plane of separation between the superior and the inferior mediastinum. The true ribs are the first seven ribs (ribs 1-7), the falsa ribs are the lower five ribs (ribs 8-12), and the floating ribs are the last two ribs (ribs 11 and 12). Flail chast occurs when a segment of the anterior or lateral thoracic wall moves freely because ofmultipla rib fractures, allowing the loose segment to move inward on inspiration and outward on expiration. Musclas of inspiration include the diaphragm; external, internal (interchondral part), and innermost intercostal muscles; sternocleidomastoid; levator costarum; serratus anterior; serratus posterior superior; scalenus; and pectoral muscles. Musclas of axpiration include anterior abdominal, internal intercostal {costal part), and serratus posterior inferior muscles. Quiet inspiration results from contraction of the diaphragm, whereas quiet expiration is a passive process caused by the elastic recoil of the lungs. The trachea begins at the inferior border of the cricoid cartilage (C6) and has 16 to 20 incomplete hyaline cartilaginous rings that prevent the trachea from collapsing and that open posteriorly toward the esophagus. It bifurcates into right and left primary bronchi at the level of the sternal angle. The carina, the last tracheal cartilage, separates the openings of the right and left primary bronchi. The right primary bronchus is shorter, wider, and more vertical than the left and divides into the superior (eparterial), middle, and inferior secondary (lobar) bronchi. The left primary bronchus divides into the superior and inferior lobar bronchi. The bronchopulmonary segment is the anatomical, functional, and surgical unit of the lungs and consists of a segmental (tertiary or lobular) bronchus, a segmental branch of the pulmonary artery, and a segment oflung tissue, surrounded by a delicate connective tissue (intersegmental) septum. The pulmonary veins are intersegmental. Bronchopulmonary (hilum) nodes drain into tracheobronchial nodes, then to paratracheal nodes, and eventually to the thoracic duct. Lung buds arise from the laryngotracheal diverticulum in the embryonic foregut region. Lungs are the essential organs of respiration. The right lung is divided into the upper, middle, and lower lo bes bythe oblique and horizontal fissures. The left Iung is divided into the upper and lower lobes by an oblique fissure and contains the lingula and the cardiac notch. Most abscesses occur in the right lung, because the right main bronchus is wider, shorter, and more vertical than the left, and thus aspirated infective agents gain easier access to the right lung. The cupu la is the dome of cervical parietal pleura over the apex of the lung. It lies above the first rib and is vulnerable to trauma at the root of the neck. Pancoast tumor (superior pulmonary sulcus tumor) is a malignant neoplasm of the lung apex, which may cause a lower trunk brachia! plexopathy and a lesion of cervical sympathetic chain ganglia with Horner syndrome (ptosis, enophthalmos, miosis, anhidrosis, and vasodilation). Chronic obstructive pulmonary disease (COPD) is an obstruction of airflow through the airways and lungs and includes chronic bronchitis and emphysema. Shortness of breath in COPD occurs when the walls of the airways and air sacs get inflamed, destroyed, lose elasticity, and hypersecrete mucus. Chronic bronchitis is an inflammation of the airways, which results in excessive mucus production that plugs up the airways, causing a cough and dyspnea (difficulty in breathing). Emphysema is an accumulation of trapped air in the alveolar sacs, resulting in destruction of the alveolar walls, reducing the surface area for gas exchange. Asthma is an airway obstruction and is characterized by dyspnea, cough, and wheezing with spasmodic contraction of smooth muscles in the bronchi and bronchioles, narrowing the airways. Barrel chest is a chest resembling the shape of a barrel because the lungs are overinflated and the thoracic cage becomes enlarged, as seen in cases of emphysema or asthma. Bronchiectasis is a chronic dilation of bronchi and bronchioles, resulting from destruction of bronchial elastic and muscular elements, which may cause collapse of the bronchioles. It may be caused by pulmonary infections or by a bronchial obstruction with heavy sputum production. Pleurisy (pleuritis) is inflammation of the pleura with exudation (escape of fluid from blood vessels) into its cavity, causing the pleural surfaces to be roughened, producing friction. Pneumothorax is an accumulation of air in the pleural cavity because of an injury to the thoracic wall or the lung, causing no negative pressure in the chest, and thus the lung collapses. Tension

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pneumothorax is a life-threatening pneumothorax in which air enters during inspiration and is trapped during expiration; therefore, the resultant increased pressure displaces the mediastinum to the opposite side, with consequent cardiopulmonary impairment. Pleura I effusion is an abnormal accumulation of excess fluid in the pleural space, having two types: the 1ransuda1e (clear watery fluid) and the exudate (cloudy viscous fluid). Thoracentesis (pleuracentesis or pleural tap) is a surgical procedure to collect pleural effusion for analysis. A needle or tube is inserted through the thoracic wall into the pleural cavity posterior to the midaxillary line one or two intercostal spaces below the tluid level but not below the ninth intercostal space. Fluid in the pleural cavity includes hydrothorax {water), hemothorax (blood), chylothorax {lymph), and pyothorax (pus). Pneumonia (pneumonitis) is an infection in the lungs, which is of bacterial, viral, or mycoplasmal origin. Tuberculosis (TB) is an infectious lung disease caused bythe bacterium Mycobacterlum tuberculo.ris and is characterized by the formation of tubercles that can undergo necrosis. Cystic fibrosis (CF) is an inherited multisystem disease that has widespread dysfunction ofthe exocrine glands and pulmonary and gastrointestinal tracts. CF affects the respiratory system by causing an excess production of viscous mucus, obstructing the respiratory airway. Pulmonary edema involves fluid accumulation in the lungs caused by lung toxins. As pressure in the pulmonaryveins rises, fluid is pushed into the alveoli and becomes a barrier to normal oxygen exchange, resulting in shortness of breath, increased heart rate, and cough. Atelectasis is the collapse of a lung by blockage of the air passages, pressure on the outside of the lung, or shallow breathing. It is caused by mucus secretions that plug the airway, foreign bodies in the airway, and tumors that compress or obstruct the airway. Lung cancer has two types: small cell and non-small cell carcinomas. Smal I cell carcinoma accounts for 20% and grows aggressively; non-small cell carcinoma {80%) is further divided into squamous cell carcinoma (most common type), adenocarcinoma, and bronchoalveolar large cell carcinoma. Pulmonary embolism is an obstruction of the pulmonary artery or one ofits branches by an embolus (air, blood clot, fat, tumor cells, or other foreign material). Its most common origin is deep leg veins (especially those in the calf). Phranic nerve supplies somatic motor fibers to the diaphragm. The central part of the diaphragm receives sensory fibers from the phrenic nerve, whereas the peripheral pa rt receives sensory fibers from the intercostal nerves. Phrenic nerve lesion may not produce complete paralysis ofthe corresponding half of the diaphragm because the accessory phrenic nerve usually joins the phrenic nerve in the root of the neck. Pain from an infection of the pericardium (pericarditis) is carried in the phrenic nerve. Pericarditis is an inflammation of the pericardium, and the typical sign is pericardia! murmur or pericardia! friction rub. Pericarditis may result in pericardia I effusion and cardiac tamponade. Pericardia I effusion is an accumulation of fluid in the pericardia! space, resulting from inflammation caused by acute pericarditis. The accumulated fluid compresses the heart, inhibiting cardiac filling. A radiograph will reveal an enlarged cardiac silhouette with a water bottle appearance. Cardiac 1amponade is an acu1e compression of 1he bean caused by a rapid accumula1ion of fluid or blood in the pericardia! cavity and can be treated by pericardiocentesis. Peri card iocentesis is a surgica I puncture of the peri cardial cavity for the aspiration of fluid. A needle is inserted into the pericardia! cavity through the fifth intercostal space left of the sternum. The crista 1ermin1lis is a vertical muscular ridge running anteriorly along the right atrial wall from the opening of the SVC to the opening of the IVC, providing the origin of the pectinate muscles. It presents the junction between the primitive sinus venosus and the right atrium proper and is indicated externally by the sulcus terminalis. The left atrium is smaller with thicker walls than the right atrium and is the most posterior of the four chambers. The left ventricle forms the heart's apex, performs harder work, has a thicker wall, and is more cone shaped than the right ventricle. The papillary muscles contract to tighten the chordae tandineae, preventing eversion ofthe AV valve cusps into the atrium, thus preventing regurgitation of ventricular blood into the atrium. The saptomarginal trabacula {moderator band) is an isolated band oftrabeculae carneae that forms a bridge between the interventricular septum and the base of the anterior papillary muscle of the right ventricle. It carries the right limb (Purkinj e fibers) of the AV bundle.

94

BRS Gross Anatomy Atrial septa I defect (ASD) is a congenital defect in the interatrial septum due to failure ofthe foramen primum or secundum to close normally, resulting in a patent foramen ovale. This defect shunts blood from the left atrium to the right atrium, thus mixing oxygenated and deoxygenated blood. A large ASD can cause hypertrophy of the right chambers and pulmonary trunk. Ventricular septal defect (VSD) occurs usually in the membranous part of the interventricular septum and is the most common congenital heart defect. The defect results in left-to-right shunting of blood through the IV foramen, increases blood flow to the lung, and causes pulmonary hypertension. The first {"lub") sound is caused by closure of the tricuspid and mitral valves at the onset of ventricular systole. The second {"dub") sound is caused by closure of the aortic and pulmonary valves and vibration of the walls of the heart and major vessels at the onset of ventricular diastole. For cardiac auscultation, the stethoscope should be placed over the mitral valve area, in the left fifth intercostal space over the apex of the heart to hear the first heart sound ("tub"). The tricuspid (right AV) valve is most audible over the right or left lower part of the body of the sternum, whereas the bicuspid or mitral {left AV) valve is most audible over the apical region of the heart in the left fifth intercostal space at the midclavicular line. The pulmonary va Ive is most audible over the left second intercostal space just lateral to the sternum, whereas the aortic valve is most audible over the right second intercostal space just lateral to the sternum. Mitra I valve stenosis is a narrowing of the orifice of the mitral valve. This impedes the flow of blood from the left atrium to the left ventricle, causing the left atrium and pulmonary edema to enlarge because of increased left atrial pressure. Mitra I valve prolapse is a condition in which the valve everts into the left atrium when the left ventricle contracts and may produce chest pain, shortness of breath, and cardiac arrhythmia. The SA node (pacemaker) initiates the heartbeat. Impulse travels from the SA node to the AV node to the AV bundle (of His), which divides into the right and left bundle branches, then to subendocardial Purkinje fibers, and the ventricular musculature. SA node is supplied by SA nodal branch of the right coronary artery. Myocardial infarction (MI) is necrosis of the myocardium due to local ischemia. Causes ofischemia includevasospasm or obstruction ofthe blood supply, most commonly due to a thrombus or embolus in a coronary artery. Major causes of MI include coronary atherosclerosis and thrombosis, and the left anterior descending artery is the most common site {40%-50%). MI symptoms range from none (silent MI) to severe chest pain or pressure for a prolonged period. Angina pectoris is characterized by chest pain originating in the heart and felt beneath the sternum, in many cases radiating to the left shoulder and down the arm. It is caused by an insuHici ant supply of oxygen to the heart muscle. It can be treated with nitroglycerin. Endocarditis is an infection of the endocardium of the heart, most commonly involving the heart valves, and is caused by a cluster of bacteria on the valves. The valves have reduced defense mechanisms because they do not receive dedicated blood supply, and thus immune cells cannot enter. Valve infections can cause cardiac murmur, which is a characteristic sound generated by turbulence ofblood flow through an orifice of the heart. Damage to Iha conducting system interferes with the spread of electrical signals through the heart (heart block). A delay or disruption ofthe electrical signals produces an irregular and slower heartbeat, reducing the heart's efficiency in maintaining adequate circulation. Severe heart block requires implantation of a pacemaker. Atrial or ventricular fibrillation is a cardiac arrhythmia resulting from rapid irregular uncoordinated contractions of the atrial or ventricular muscle. Fibrillation causes palpitations, shortness of breath, angina, fatigue, congestive heart failure, and sudden cardiac death. Coronary atherosclerosis is characterized by the presence of sclerotic plagues containing cholesterol and lipid material that impairs myocardial blood flow, leading to ischemia and MI. Coronary angioplasty is an angiographic reconstruction of a blood vessel made by enlarging a narrowed coronary arterial lumen. It is performed by peripheral introduction of a balloon-tip catheter and dilation of the arterial lumen on withdrawal of the inflated catheter tip. Coronary bypass is the connection of a healthy section ofvessel (usually the saphenous vein or internal thoracic artery) between the aorta and a coronary artery distal to an obstruction. Alternatively, the internal thoracic artery is connected to the coronary artery distal to the obstructive lesion. Bypass creates a new pathway for blood flow to the heart muscle.

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Aortic aneurysm is a local dilation of the aorta that can lead to dissection or rupture. If located in the aortic arch, compression of the left recurrent laryngeal nerve may occur, leading to coughing, hoarseness, and paralysis of the ipsilateral vocal cord. Pressure on the esophagus may cause dysphagia (difficulty in swallowing), whereas dyspnea (difficulty in breathing) results from pressure on the trachea, root of the lung, or phrenic nerve. Marian syndrome is an inheritable disorder of connective tissue. It most often affects the heart and blood vessels (aortic root dilation, aortic aneurysm, aortic regurgitation, and mitral valve prolapse), the skeleton (long limbs), eye (dislocated lens), and lungs (spontaneous pneumothorax). The coronary arteries arise from the ascending aorta. Systolic compression ofthe arterial branches in the myocardium reduces coronary blood flow. Therefore, maximal blood flow occurs during diastole. The right coronary artery has the SA nodal, marginal, posterior Iv, and AV nodal branches. The left coronary artery is shorter than the right one and divides into the anterior N and circumflex arteries. All cardiac veins, including the great, middle, small, and oblique cardiac veins, drain into the coronary sinus except the anterior cardiac vein, which drains into the right atrium. Tetralogy of Fallot includes {I) pulmonary stenosis (narrowing of right ventricular outflow), (2) large overriding aona (drains both ventricles), (3) VSD, and (4) right ven1ricular hypertrophy. Itis characterized by right-to-left shunting of blood and cyanosis. Overriding aorta (dextroposition of aorta) is that the aorta (its outlet) lies over both ventricles (instead of just the left ventricle), directly above the VSD, causing the aorta to arise from both ventricles. Transposition of the great vessels occurs when the AP septum fails to develop in a spiral fashion, causing the aorta to arise from the right ventricle and the pulmonary trunk to arise from the left ventricle. Patent ductus arteriosus results from failure of the ductus arteriosus to close after birth and is common in premature infants. The duclus arteriosus takes origin from the left sixth aortic arch. The fourth aortic arches contribute to the right subclavian artery on the right side and the aortic arch on the left. The mediastinum is an interpleural space and consists of the superior mediastinum and inferior mediastinum. The inferior mediastinum further divides into the anterior, middle, and posterior mediastina. The middle mediastinum contains the heart. The posterior mediastinum contains the esophagus, thoracic aorta, azygos and hemiazygos veins, thoracic duct, vagus nerves, and sympathetic splanchnic nerves. Achalasia is a condition of impaired esophageal contractions resulting from degeneration of myenteric (Auerbach) plexus in the esophagus. The lower esophageal sphincter fails to relax during swallowing. Systemic sclerosis (scleroderma) is a systemic collagen vascular disease and has clinical features of dysphagia for solids and liquids, severe heartburn, and esophageal stricture. Coarcta1ion of the aorta occurs when the aorta is abnormally constricted just inferior to the ductus arteriosus, in which case an adequate collateral circulation develops before birth. Clinical signs include hypertension and/or heart failure. It causes (a) a characteristic rib notching and a high risk of cerebral hemorrhage; (b) tortuous and enlarged blood vessels, especially the internal thoracic, intercostal, epigastric, and scapular arteries; (c) an elevated blood pressure in the radial artery and decreased pressure in the femoral artery; and (d) the femoral pulse to occur after the radial pulse (normally the femoral pulse occurs slightly before the radial pulse). SteIlate block is an injection of local anesthetic near the stellate ganglion administered by placing the tip ofthe needle near the neck of the first rib. It produces a temporary interruption of sympathetic function such as in a patient with excess vasoconstriction in the upper limb. Injury to the recurrent laryngeal nerve may be caused by a bronchogenic or esophageal carcinoma, enlargement ofmediastinal lymph nodes, an aneurysm of the aortic arch, or thyroid and parathyroid surgeries, causing respiratory obstruction, hoarseness, or an inability to speak because of paralysis of the vocal cord. Vagotomy is transection of the vagus nerves at the lower portion of the esophagus in an attempt to reduce gastric secretion in the treatment of peptic ulcer. The azygos vein is formed by the union of the right ascending lumbar and right subcostal veins. Its lower end is connected to the IVC. It arches over Iha root of the right lung and empties into the SVC. The hemiazygos vein is formed by the union of the left subcostal and ascending lumbar vein, receives the 9th, 10th, and 11th posterior intercostal veins, and enters the azygos vein. Its lower end is

96

BRS Gross Anatomy connected to the left renal vein, The accessory hemiazygos vein receives the fifth to eighth posterior intercostal veins and terminates in the azygos vein. The superior intarcostal vein is formed by the second, third, and fourth intercostal veins and drains into the azygos vein on the right and the brachiocephalic vein on the left. The thoracic duct begins in the abdomen at the cistarna chyl i, which is the dilated junction of the intestinal, lwnbar, and descending intercostal trunks. It drains all parts of the body except the right head, neck, upper limb, and thorax, which are drained by the right lymphatic duct. It passes through the aortic opening of the diaphragm, ascends between the aorta and the azygos vein, and empties into the junction of the left internal jugular and subclavian veins. The greater splanchnic nerve arises from the fifth through ninth thoracic sympathetic ganglia and ends in the celiac ganglion. The lesser splanchnic nerve arises from the 10th and 11th thoracic sympathetic ganglia and ends in the aorticorenal ganglion. The least splanchnic nerve arises from the 12th thoracic sympathetic ganglion and ends in the renal plexus. All ofthese splanchnic nerves contain preganglionic sympathetic visceral efferent (VE) fibers with cell bodies located in the lateral horn (intermediolateral cell colwnn) of the spinal cord and VA fibers with cell bodies located in the dorsal root ganglia. White rami commun icantes contain preganglionic sympathetic VE fibers with cell bodies located in the lateral horn of the spinal cord and VA fibers with cell bodies located in the dorsal root ganglia. They are connected to the spinal nerves and limited to spinal cord segments between Tl and L2. Gray rami communicantes contain postganglionic sympathetic VE fibers with cell bodies located in the sympathetic chain ganglia. They are connected to every spinal nerve and supply the blood vessels, sweat glands, and arrector pili muscles of hair follicles. Autonomic nerve functions in the thorax:

Functions of Autonomic Nerves Hean Bronchi Esophagus

Sympathetic Nerva

Parasympathetic Nerva

Increases rate and ventricular contraction; dilates coronary vessels Dilatas lumen; reduces bronchial secretion Vasoconstriction

Decreases rate and ventricular contraction; constricts coronary vessels Constricts lumen; promotes sec ration Peristalsis

Review Test

Direc1ian1: Each of th.e numbered items or incomplete statements in this section is followed by answers or by rompletions of the statement Select the Dne-lettered answer or completion that is bHt in each cue. 1. A 32-year-old patient who weighs 275 lb

(Al Dorsal root ganglion and anterior horn of

comes to the doctor's ofllce. On the surface of the chest, the phylldan is able to locate the apex or the heart:

the spinal cord (B) Sympathetic chain ganglion and dorsal root ganglion (C) Sympathetic chain ganglion and posterior horn of the spinal cord (D) Dorsal root ganglion and lateral horn of the spinal cord IE) Anterior and lateral horns of the spinal cord

(A) At the level or the sternal angle (B) In the left fourth intercostal space (C) In the left filth intercostal space (D) In the right fifth intercostal space (E) At. the level of the xl.phoid process or the

sternum

Z. A 43-year-old female had been lying down on the hospital bed for more than 4 months. Her normal. quiet ~iration is achieved by contraction of which of the following structure&?

5. A 27-year-old cardiac patient with an irregular heartbeat vlslta her doctor's ofllce for examination. Where should the physician place the stethoacope to 11.sten to the sound of the mltral valve?

(A) mastic tissue in the lungs and thoracic wall (B) Serratu.s potterlor superiormuscle8 (C) Pectorall1 minor muacles (D) Serratus anterior mu.scle1 (E) Diaphra,gm

IA)

!. A 23-year-old man suffered a gunshot

IDI

Over the medial end of the second left lntercostal space (B) Over the medial end or the second right intercostal. apace (C) In the left fourth intercoatal apace at the

midclmcular line wound, and his greater splanchnic nerve wu destroyed. Which of the following nerve fibers would be injured?

(A) Somatic afferent {SA) and preganglionic sympathetic fib en

(I) Visceral afferent (VA) and postganglionic sympathetic fibers (C) VA and preganglionic sympathetic fibers (D) Somatic efferent (SB) and postganglionic sympathetic fibers (E) VA and SE fibers

4. A 17-year-old boywu involved in a gang fight, and a stab wound severed the white rami communicantel at the level of bia sixth thoracic 'Vertebra. Thia infurywould result in degeneration of nerve cell bodies in which of the following structures?

In the left fifth intercostal space at the mid-

clavicular line (E) Over the right half of the lower end of the body of the sternum

&. A 19-year-old man waa brought to the emergency department after a motor vehlcl.e accident, and his anglogram exhibited that he was bleeding from the vein that is accompanied by the posterior interventrlcular artery. Which of the foll.owing veins is most likely to be ruptured? IA) Great cardiac vein IB) Middle cardiac vein ICI Anterior cardiac vein IDI Small cardiac vein (E) Oblique veins of the left atrium

98

BRS Gross Anatomy

1. A 37-year-old patient with chronic intermittent palpitation was examined by her physician, and one of the diagnostic studies included a posterior-anterior chest radiograph. Which of the following comprises the largest portion of the sternocostal surface of the heart seen on the radiograph? (Al Left atrium (BJ Rightatrium (Cl Left ventricle (DJ Rightventricle (El Base of the heart 8. A 5-year-old girl is brought to the emergency department because of difficulty breathing, palpitations, and shortness of breath. Doppler study of the heart reveals an atrial septal defect {ASD). This malformation usually results from incomplete closure of which of the following embryonic structures? (AJ Ductus arteriosus (BJ Ductus venosus (C) Sinus venarum (DI Foramen ovale (El Truncus arteriosus

9. A 54-year-old patient with amyloidosis and subsequent cardiac dysrhythmias undergoes implantation with an artificial cardiac pacemaker. Which of the following conductive tissues of the heart was defective in function that required the pacemaker?

(Al (Bl (C) (DJ (El

Atrioventricular (AV) bundle AVnode Sinoatrial (SA) node Purkinje fiber Moderator band

11. The bronchogram of a 45-year-old female smoker shows the presence of a tumor in the eparterial bronchus. Which airway is most likely blocked? (Al Left superior bronchus (Bl Left inferior bronchus (Cl Right superior bronchus (DJ Right middle bronchus (E) Right inferior bronchus 12. An 83-year-old man with a previously normal coronary circulation is now having symptoms from an embolism of the circumflex branch of the left coronary artery. This condition would result in ischemia of which of the following areas of the heart? (Al Anterior part of the left ventricle (BJ Anterior interventricular region (Cl Posterior interventricular region (DI Posterior part of the left ventricle (E) Anterior part of the right ventricle 13. A 44-year-old man with a stab wound was brought to the emergency department, and a physician found that the patient was suffering from a laceration of his right phrenic nerve. Which of the following conditions has likely occurred? (Al Injury to only somatic efferent (SE) fibers (Bl Difficulty in expiration (Cl Loss of sensation in the fibrous pericardium and mediastinal pleura (D) Normal function of the diaphragm (El Loss of sensation in the costal part of the diaphragm

14. An 8-year-old boy with an ASD presents to

lobar (secondary) bronchus along with lung tissue from a 57-year-old heavy smoker with lung cancer. Which of the following bronchopulmonary segments must contain cancerous tissues?

his pediatrician. This congenital heart defect shunts blood from the left atrium to the right atrium and causes hypertrophy of the right atrium, right ventricle, and pulmonary trunk. Which of the following veins opens into the hypertrophied atrium?

(Al (BJ (Cl (DI (El

(Al Middle cardiac vein (B) Small cardiac vein (Cl Oblique cardiac vein (D) Anterior cardiac vein (El Right pulmonary vein

10. A thoracic surgeon removed the right middle

Medial and lateral Anterior and posterior Anterior basal and medial basal Anterior basal and posterior basal Lateral basal and posterior basal

l!iJtf:lOil 15. A 37-year-oldpatientwith severe chest pain, shortness of breath, and congestive heart failure was admitted to a local hospital. His coronary angiogram reveals thrombosis in the circumflex branch of the left coronary artery. Which of the following conditions could result from the blockage of blood flow in the circumflex branch? (A) Tricuspid valve insufficiency (B) Mitral valve insufficiency (C) Ischemia of AV node (D) Paralysis ofpectinate muscle (E) Necrosis of septomarginal trabecula

16. A 75-year-old patient has been suffering from lung cancer located near the cardiac notch, a deep indentation on the lung. Which of the following lobes is most likely to be resected?

(A) Superior lobe of the right lung (B) Middle lobe of the right lung (C) Inferior lobe of the right lung (D) Superior lobe of the left lung (E) Inferior lobe of the left lung 17. A thoracentesis is performed to aspirate an abnormal accumulation of fluid in a 37-yearold patient with pleural effusion. A needle should be inserted at the midaxillary line between which of the following two ribs to avoid puncturing the lung?

(A) Ribs I and 3 (B) Ribs 3 and 5 (C) Ribs 5 and 7 (D) Ribs 7 and 9 (E) Ribs 9 and 11

18. A newborn baby is readmitted to the hospital with hypoxia and, upon testing, is found to have pulmonary stenosis, dextroposition of the aorta, interventricular septal defect, and hypertrophy of the right ventricle. Which of the following is best described by these symptoms?

(A) ASD (B) Patent ductus arteriosus (C) Tetralogy of Fallot (D) Aortic stenosis (E) Coarctation of the aorta diac catheterization lab for sudden occlusion at the origin of the descending (thoracic) aorta. Titls condition would most likely decrease

99

blood flow in which of the following intercostal arteries? (A) Upper six anterior (B) All of the posterior (C) Upper two posterior (D) Lower anterior (El Lower six posterior

20. A 56-year-old patient recently suffered a myocardial infarction of the apex of the heart. The occlusion by atherosclerosis is in which of the following arteries?

(Al Marginal artery (B) Right coronary artery at its origin (C) Anterior interventricular artery (DI Posterior interventricular artery (El Circumflex branch of the left coronary artery 21. A 75-year-old woman was admitted to a local hospital because a chest radiograph revealed a left lung mass and bronchoscopy revealed lung carcinoma. Which of the following structures or characteristics does the cancerous lung contain?

(Al Horizontal fissure (Bl Groove for superior vena cava (SVC) (C) Middle lobe

(DJ Lingula (El Larger capacity than the right 22. An 18-year-old girl is thrust into the steering wheel after her car hits the vehicle in front of her and stops suddenly. She then experiences difficulty in (forced) expiration. Which of the following muscles is most likely damaged? (Al Levator costarum (Bl Innermost intercostal muscle (C) External intercostal muscle

(DI Diaphragm (El Muscles of the abdominal wall 23. A 78-year-old patient presents with advanced cancer in the posterior mediastinum. The surgeons are in a dilemma as to how to manage the condition. Which of the following structures is most likely damaged?

(Al Brachiocephalic veins 19. A 33-year-old patient is brought to the car-

Thorax

(BJ Trachea (C) Arch of the azygos vein (D) Arch of the aorta

(El Hemiazygos vein

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BRS Gross Anatomy

24. A 46-year-old man comes to his doctor's office and complains of chest pain and headache. His computed tomography (CT) scan reveals a tumor located just superior to the root of the right lung. Blood flow in which of the following veins is most likely blocked by this tumor?

IAI IBI

Hemiazygos vein Arch of the azygos vein IC) Right subclavian vein ID I Right brachiocephalic vein IE) Accessory hemiazygos vein

25. A 21-year-old patient with a stab wound reveals a laceration of the right vagus nerve proximal to the origin of the recurrent laryngeal nerve. Which of the following conditions would most likely result from this lesion?

IAI IBI

Contraction of bronchial muscle Stimulation of bronchial gland secretion IC) Dilation of the bronchial lumen ID) Decrease in cardiac rate IE) Constriction of coronary artery

26. A neonate appears severely cyanotic and breathes rapidly. Cardiac echocardiogram reveals the aorta lies to the right of the pulmonary trunk. Which of the following is most likely to have occurred during development?

IAI

AP septum failed to develop in a spiral fashion IBI Excessive resorption of septum primum IC) Pulmonary valve atresia ID) Persistent truncus arteriosus IE) Coarctation of the aorta

XI. A 12-year-old boy was admitted to a local hospital with complications from his congenital heart disease, including left ventricular hypertrophy, which could have resulted from which of the following conditions?

IAI IBI

A constricted pulmonary trunk An abnormally small left AV opening IC) Improper closing of the pulmonary valves ID I An abnormally large right AV opening IE) Stenosis of the aorta

28. A 31-year-old man was involved in a severe automobile accident and suffered laceration of the left primary bronchus. The damaged primary bronchus:

IAI IBJ

Has a larger diameter than the right primary bronchus Often receives more foreign bodies than the right primary bronchus

IC) Gives rise to the eparterial bronchus IOI Is longer than the right primary bronchus IE) Runs under the arch of the azygos vein 29. A 62-year-old woman who is a heavy smoker has an advanced lung cancer that spread into her right third posterior intercostal space posterior to the midaxillary line. If cancer cells are carried in the venous drainage, they would travel first to which of the following veins?

IA) IB)

SVC Right superior intercostal vein IC) Right brachiocephalic vein ID) Azygos vein IE) Hemiazygos vein

30. A radiologist reviews the chest radiographs of a 27-year-old victim of a car accident. Which of the following structures forms the right border of the cardiovascular silhouette?

IA)

Arch of the aorta (B) Pulmonary trunk (C) SVC (D) Ascending aorta (E) Left ventricle

31. A 37-year-old man is brought to the emergency department complaining of severe chest pain. His angiogram reveals thromboses of both brachiocephalic veins just before entering the SVC. This condition would most likely cause a dilation of which of the following veins?

IA)

Azygos

(B) Hemiazygos (C) Right superior intercostal (D) Left superior intercostal (E) Internal thoracic 32. A cardiologist is on clinical rounds with her medical students. She asks them, "During the cardiac cycle, which of the following events occurs?"

IA)

AV valves close during diastole

(B) Aortic valve closes during systole (C) Pulmonary valve opens during diastole (D) Blood flow in coronary arteries is maximal during diastole (E) Aortic valve closes at the same time as AV valve

l!iJtf:lOil 33. Coronary angiograms of a 44-year-old man reveal an occlusion of the circumflex branch of the left coronary artery, which leads to myocardial infarction in which of the following areas? (A) Right and left ventricles (B) Right and left atria (C) Interventricular septum (D) Apex of the heart (E) Left atrium and ventricle

34. A patient has a small but solid tumor in the mediastinum, which is confined at the level of the sternal angle. Which of the following structures would most likely be found at this level? (A) Bifurcation of the trachea (B) Beginning of the ascending aorta (C) Middle of the aortic arch (D) Articulation of the third rib with the sternum (E) Superior border of the superior mediastinum

35. A 37-year-old house painter fell from a ladder and fractured his left third rib and the structures with which it articulated. Which of the following structures would most likely be damaged? (A) Manubrium of the sternum (B) Body of the second thoracic vertebra (C) Spinous process of the third thoracic vertebra (D) Body of the fourth thoracic vertebra (E) Transverse process of the second thoracic vertebra

36. A 45-year-old woman presents with a tumor confined to the posterior mediastinum. This could result in compression ofwhich of the following structures? (A) Trachea (B) Descending aorta (C) Arch of the aorta (D) Arch of the azygos vein (E) Phrenic nerve

37. A 62-year-old patient with pericardia! effusion comes to a local hospital for aspiration of pericardia! fluid by pericardiocentesis. Which of the following intercostal spaces adjacent to the

Thorax

101

sternum would be best for insertion of a needle into the pericardia! cavity? (A) Right fourth intercostal space (B) Left fourth intercostal space (C) Right fifth intercostal space (D) Left fifth intercostal space (El Right sixth intercostal space

38. The attending physician in the coronary intensive care unit demonstrates to his students a normal heart examination. The first heart sound is produced by near-simultaneous closure of which of the following valves? (A) Aortic and tricuspid (B) Aortic and pulmonary (C) Tricuspid and mitral (D) Mitral and pulmonary (El Tricuspid and pulmonary 39. A 27-year-old patient with Marfan syndrome has an aneurysm of the aortic arch. This may compress which of the following structures? (A) Right vagus nerve (B) Left phrenic nerve (C) Right sympathetic trunk (D) Left recurrent laryngeal nerve (El Left greater splanchnic nerve 40. A 47-year-old man with a known history of chronic atrial fibrillation returns to see his cardiologist for follow-up of his cardiac health. The right atrium is important in this case because it: (A) Receives blood from the oblique cardiac vein (B) Is associated with the apex of the heart (C) Contains the SA node (D) Receives the right pulmonary vein (El Is hypertrophied by pulmonary stenosis

41. A 57-year-old patient has a heart murmur resulting from the inability to maintain constant tension on the cusps of the AV valve. Which of the following structures is most likely damaged? (A) Crista terminalis (B) Septomarginal trabecula (C) Chordae tendineae (D) Pectinate muscle (El Annulus fibrosus

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42. A mother with diabetes gives birth to a baby who is diagnosed as having dextroposition of the aorta and the pulmonary trunk with cyanoais and ahortness of breath. Which of the fol· lowing structure& la required to remain patent untll aurgtcal correction of the deformity?

cartilages are deriwd from which of the following derivations?

(A) Umbilical arterie& (B) Umbillcal vein (C) Ductu& arterlosus (D) Ductua venosua (E) Sinua venosus

(El Neuroectoderm

43. During early development of the respira-

(Al (BJ

Bctoderm Mesoderm (C) Endoderm

(DJ Proctodeum

Qulllians 47 ta 52: Choosa the eppropriat1 lllttBr1d site or structure in this CT seen (see figure below) of the thorax of a 42-year-old men who complains of chest pain and breathing problems. His electrocardiogram shows left ventricular hypertrophy.

tory aystem, the laryngotracheal tube maintains communication with the primitive foregut. Which of the following embryonic structures is most likely responsible for partitioning these two embryonic structures? Tracheoesophageal folds Tracheoesophageal fistula Tracheoesophageal septum Laryngotracheal divertlculum (El Laryngotracheal aeptum

(A) (B) (C) (D)

44. A 32-year-old woman has a tension pneumothoiu while ldck bCDing. lt la determined that It can be treated with needle up.i ration. To .void an injury of the inmroostal neumvascular bundle, the needle may be inserted in which of the following locations? (A) Above the upper border of the rlbs (I) Deep to the upper border of the ribs (C) Beneath the lower border of the ribs (D) Between the external and internal

47. Stenosis ofwhich structure may produce left ventricular hypertrophy? 41. Which structure la moat likely to be removed by a surgical oncologist in a aurgical resection of a lobe (lobectomy) to remove hmg cancer in the apa of the right lung?

49. From which structure do the bronchial arteriea arise?

intercostals (E) Through the tramversus thoracis muscle

50. Into whl.ch structure does the azygos vein drain venous blood?

45. A 9-month-old girl waa admitted to the local children's hospital with tachypnea (fast breathing) and shortneaa of breath. Physical examination further emtbits tachycardia (fast heart rate), a bounding peripheral pulse, and her anglographs reveal a patent ductus arteriosus. Which of the following embryonic arterial structures is most likely responsible for the origin of the patent ductus arterioaus?

51. The left coronary artery arises from which

(A) Right fourth arch (I) Left fifth arch

(C) Right fifth arch (D) Left sixth arch (E) Right sixth arch

structure?

52. Which structure la croased superiorly by the aortic arch and left pulmonary artery'?

Qulllions 53 ta 51: Choosa the eppropriat1 lllttBr1d site or structure in this CT seen (see figure below) of the thorax. Which structure in this CT scan:

A I

46. A 7-day-old neonate la diagnosed aa having congenital neonatal emphysem~ which is caused by collapsed bronchi because of failure of bronchial certllage development. Bronchial

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103

53. Can be removed in a surgical resection of

56. Lles on the right side of the aortic arch and

a lobe to remove lung cancer on the diaphragmatic surface?

ascending aorta?

57. Contains the septomarginal trabecula 54. Becomes hypertrophied as result of the pulmonary stenosis?

(moderator band)?

58. Takes its origin from the left ventricle and 55. Receives oxygenated blood via pulmonary veins?

ends at the sternal angle?

Answers and Explanations 1. The answer is C. (Pericardium. and Heart: II.A) On the surface of the chest, the apex of the heart

2.

3. 4.

5.

&.

1.

8.

9.

10.

104

can be located in the left fifth intercostal space slightly medial to the midclavicular (or nipple) line. The sternal angle is located at the level where the second ribs articulate with 1he stemum. The lliphoid process lies atthe level of the TIO vertebra. The answer is A. (Mediastinum, Pleura, and Organs ofRespiration: V.B) Normal, quiet expiration is achieved by contraction of extensible tissue in the lungs and the thoracic wall. The serratus posterior superior muscles, diaphragm, pectoralis major, and selT8tus anterior are muscles of inspiration. The answer is C. (Structures in the Posterior Mediastinum: 111.A.3.(a)) The greater splanchnic nerves contain VA and preganglionic sympathetic visceral efferent (VE) fibers. The answer is D. (Autonomic Nervous System in the Thorax: A.2.a) The white rami communicantes contain pregangllonic sympathetic VE fibers and VA fibers, whose cell bodies are located in the lateral horn of the spinal cord and the dorsal root ganglia. The sympathetic chain ganglion contains cell bodies of the postganglionic sympathetic nerve fibers. The anterior horn of1he spinal cord contains cell bodies of the SB fibers. The dorsal root ganglion contains cell bodies of both SA and VA fibers. The answer is D. (Pericardium. and Heart: C.4) Themitralvalve (leftAVvalve)producesthe apical beat (thrust) of the heart, which is most audible over the left fifth intercostal space at the midcla:vicular line. The pulmonary valve is most audible over the medial end of the second left intercostal space; 1he aortic valve is most audible over the medial end of the second right intercostal space; and the right AV valve is most audible over the right half of the lower end of the body of the sternum. The answer is B. (Pericardium. and Heart: ll.G.3) The middle cardiac vein ascends in the posterior interventricular groove, accompanied by the posterior interventricular branch of the right coronary artery. The great cardiac vein is accompanied by the anterior interventricular artery; the anterior cardiac vein drains directly into 1he right atrium; and the small cardiac vein is accompanied by the marginal artery. The answer is D. (Pericardium and Heart: n.B.3) The right ventricle forms a large part of the stemocostal surface of the heart The left atrium occupies almost the entire posterior surface of the right atrium. The right atrium occupies the right aspect or the heart The left ventricle Iles at the back of the heart and bulgea roundly to the left The base of the heart Is formed by the atria, which lie mainly behind the ventricles. The answer is D. (Perlcardlum and Heart: Iv.C.2) An ASD is a congenital defect in the interatrlal septum. During partitioning of the two atria, the opening in the foramen secundum (the foramen ovate) usually closes at birth. If this foramen ovale is not closed completely, this would result in an ASD, shunting blood from the left atrlwn to the right atrium. The answer is C. (Pericardium and Heart: ll.E.l) The SA node initiates the lmpu:tse of contraction and is known as the pacemaker of the heart. Impulses from the SA node travel through the atrial myocardium to the AV node and then race through the AV bwulle (bundle of His), which divides into the right and left bundle branches. The bundle breaks up into terminal conducting fibers (Purk:inje fibers) to spread out into the ventricular walls. The moderate band carries the right limb of the AV bundle from the septum to the stemocostal wall of the ventricle. The answer is A. (Figure 3.3) The right middle lobar (secondary) bronchus leads to the medial and lateral bronchopulmonary segments. The right superior lobar bronchus divides into the superior, posterior, and anterior segmental (tertiary) bronchi. The right inferior lobar bronchus has the anterior, lateral, posterior, and anterior segmental bronchi.

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105

11. The answer is C. (Mediastinum, Pleura, and Organs of Respiration: 11.B) The eparterial bronchus is the right superior lobar (secondary) bronchus; all of the other bronchi are hyparterial bronchi.

12. The answer is D. (Pericardium and Heart: 11.F.2.b) The left marginal branch of the circumflex branch of the left coronary artery supplies the posterior portion of the left ventricle. The anterior interventricular artery supplies the anterior aspects of the right and left ventricles and the anterior interventricular septum.

13. The answer is C. (Mediastinum, Pleura, and Organs of Respiration: VIII.B) The phrenic nerve supplies the pericardium, mediastinal and diaphragmatic (central part) pleura, and the diaphragm. It contains SE, SA, and VE (postganglionic sympathetic) fibers. The costal part of the diaphragm receives SA fibers from the intercostal nerves.

14. The answer is D. (Pericardium and Heart: 11.G.6) The anterior cardiac vein drains into the right atrium. The middle, small, and oblique cardiac veins drain into the coronary sinus. The right and left pulmonary veins drain into the left atrium.

15. The answer is B. (Pericardium and Heart: 11.F.2.b) The circumflex branch of the left coronary artery supplies the left ventricle, and thus its blockage of blood flow results in necrosis of myocardium in the left ventricle, producing mitral valve insufficiency. The tricuspid valve, AV node, pectinate muscles, and septomarginal trabecula are present in the right atrium and ventricle.

16. The answer is D. (Mediastinum, Pleura, and Organs of Respiration: IY.B) The cardiac notch is a deep indentation of the anterior border of the superior lobe of the left lung. Therefore, the right lung is not involved.

17. The answer is D. (Mediastinum, Pleura, and Organs of Respiration: III.B) A thoracentesis is performed for aspiration of fluid in the pleural cavity at or posterior to the midaxillary line, one or two intercostal spaces below the fluid level but not below the ninth intercostal space and, therefore, between ribs 7 and 9. Other intercostal spaces are not preferred.

18. The answer is C. (Pericardium and Heart: IY.C. Clinical Correlates) TetralogyofFallot is a combination of congenital cardiac defects consisting of (a) pulmonary stenosis, (b) dextroposition of the aorta (so that it overrides the ventricular septum and receives blood from the right ventricle), (c) ventricular septal defect (VSD), and (d) right ventricular hypertrophy. ASD is a congenital defect in the atrial septum, resulting from a patent foramen ovale. Patent ductus arteriosus shunts blood from the pulmonary trunk to the aorta, bypassing the lungs. Aortic stenosis is an abnormal narrowing of the aortic valve orifice, impeding the blood flow. Coarctation of the aorta is a congenital constriction of the aorta, commonly occurs just distal to the left subclavian artery, causing upper limb hypertension and diminished blood flow to the lower limbs and abdominal viscera.

19. The answer is E. (Structures in the Posterior Mediastinum: II.A) The first two posterior intercostal arteries are branches of the highest (superior) intercostal artery of the costocervical trunk; the remaining nine branches are from the thoracic aorta. The internal thoracic artery gives off the upper six anterior intercostal arteries and is divided into the superior epigastric artery and the musculophrenic artery, which gives off anterior intercostal arteries in the 7th, 8th, and 9th intercostal spaces and ends in the 10th intercostal space, where it anastomoses with the deep circumflex iliac artery.

20. The answer is C. (Pericardium and Heart: 11.F.2.a) The apex of the heart typically receives blood from the anterior interventricular branch of the left coronary artery. The right marginal artery supplies the right inferior margin of the right ventricle; the right coronary artery at its origin sup· plies the right atrium and ventricle; and the posterior interventricular artery and a circumflex branch of the left coronary artery supply the left ventricle.

21. The answer is D. (Mediastinum, Pleura, and Organs of Respiration: IY.B) The lingula is the tongue-shaped portion of the upper lobe of the left lung. The right lung has a groove for the hor· izontal fissure, superior vena cava (SVC), and middle lobe and has a larger capacity than the left lung.

22. The answer is E. (Mediastinum, Pleura, and Organs of Respiration: V.B) The abdominal muscles are the muscles of forced expiration, whereas the other distractors are muscles of inspiration.

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BRS Gross Anatomy

23. The answer is E. (Mediastinum, Pleura, and Organs of Respiration: I.D) The hemiazygos vein is located in the posterior mediastinum. The brachiocephalic veins, trachea, and arch of the aorta are located in the superior mediastinum, whereas the arch of the azygos vein is found in the middle mediastinum.

24. The answer is B. (Mediastinum, Pleura, and Organs of Respiration: II.BJ The azygos vein arches over the root of the right lung and empties into the SVC. Other veins do not pass over the root of the right lung.

25. The answer is C. (Mediastinum, Pleura, and Organs ofRespiration: VIII.A) The parasympathetic nerve fibers in the vagus nerve constrict the bronchial lumen, contract bronchial smooth muscle, stimulate bronchial gland secretion, decrease heart rate, and constrict the coronary artery. The vagus nerve also carries afferent fibers of pain, cough reflex, and stretch of the lung (during inspiration). 26. The answer is A. (Pericardium and Heart: IY.C. Clinical Correlates) Failure of the aorticopulmonary (AP) septum results in transposition of the great vessels, exhibiting that the aorta is to the right of the pulmonary trunk. Cyanosis is common in transposition of the great vessels. Excessive resorption of the septum primum results in a secundum type of ASD. Pulmonary valve atresia may result in cyanosis, but it will not cause the aorta to be to the right of the pulmonary trunk. A persistent truncus arteriosus is caused by lack of development of the AP septum, resulting in a single outflow track. Coarctation of the aorta is a severe narrowing of the aorta. ZI. The answer is E. (Structures in the Posterior Mediastinum: II.A. Clinical Correlates, Figure 3.18) Stenosis of the aorta can cause left ventricular hypertrophy. Right ventricular hypertrophy may occur as a result of pulmonary stenosis, pulmonary and tricuspid valve defects, or mitral valve steno sis.

28. The answer is D. (Mediastinum, Pleura, and Organs of Respiration: II.BJ The right primary bronchus is shorter than the left one and has a larger diameter. More foreign bodies enter it via the trachea because it is more vertical than the left primary bronchus. The right primary bronchus runs under the arch of the azygos vein and gives rise to the eparterial bronchus. 29. The answer is B. (Structures in the Posterior Mediastinum: Il.B.4, Figure 3.19) The superior intercostal vein is formed by the union of the second, third, and fourth posterior intercostal veins and drains into the azygos vein on the right and the brachiocephalic vein on the left. The azygos vein drains into the SVC. The hemiazygos vein usually drains into the azygos vein. 30. The answer is C. (Pericardium and Heart: II.A) A cardiovascular silhouette or cardiac shadow is the contour of the heart and great vessels seen on posterior-anterior chest radiographs. Its right border is formed by the SVC, right atrium, and inferior vena cava; its left border is formed by the aortic arch (aortic knob), pulmonary trunk, left auricle, and left ventricle. The ascending aorta becomes the arch of the aorta and is found in the middle of the heart. 31. The answer is D. (Structures in the Posterior Mediastinum: Il.B.4, Figure 3.19) The left superior intercostal vein is formed by the second, third, and fourth posterior intercostal veins and drains into the left brachiocephalic vein. The right superior intercostal vein drains into the azygos vein, which in turn drains into the SVC. The hemiazygos vein drains into the azygos vein, whereas the internal thoracic vein empties into the brachiocephalic vein. 32. The answer is D. (Pericardium and Heart: 11.C.3) During diastole, the AV valve is open, and the aortic and pulmonary valves close; whereas during systole, the AV valves close, and the aortic and pulmonary valves open. 33. The answer is E. (Pericardium and Heart: 11.F.2.b) The left atrium and ventricle receive blood from the circumflex branch of the left coronary artery. The interventricular septum and the apex of the heart are supplied by the anterior interventricular branch of the left coronary artery. The right ventricle receives blood from the anterior interventricular artery and the marginal branch of the right coronary artery. The right atrium receives blood from the right coronary artery. 34. The answer is A. (Thoracic Wall: I.A.2) The sternal angle is the junction of the manubrium and the body of the sternum. It is located at the level where the second rib articulates with the

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107

sternum, the trachea bifurcates into the right and left bronchi, and the aortic arch begins and ends. It marks the end of the ascending aorta and the beginning of the descending aorta, and it forms the inferior border of the superior mediastinum.

35. The answer is B. (Thoracic Wall: I.A.3, and B.1) The third rib articulates with the body of the sternum, bodies of the second and third thoracic vertebrae, and transverse process of the third thoracic vertebra.

36. The answer is B. (Mediastinum, Pleura, and Organs of Respiration: I.D) The descending (thoracic) aorta is found in the posterior mediastinum. The superior mediastinum contains the trachea and arch of the aorta, and the middle mediastinum contains the ascending aorta, arch of the azygos vein, and main bronchi. The phrenic nerve runs in the middle mediastinum.

37. The answer is D. (Pericardium and Heart: I.C, Clinical Correlates) To aspirate pericardial fluid, the needle should be inserted into the pericardial cavity through the fifth intercostal space just left of the sternum. Because of the cardiac notch, the needle misses the pleura and lungs, but it penetrates the pericardium. Lung tissues lie beneath the fourth and sixth intercostal spaces.

38. The answer is C. (Pericardium and Heart: 11.C) The first heart sound ("lubu) is produced by the closure of the tricuspid and mitral valves, whereas the second heart sound (•dub") is produced by the closure of the aortic and pulmonary valves.

39. Tha answer is D. (Structures in the Posterior Mediastinum: III.B.2) The left recurrent laryngeal nerve loops around the arch of the aorta near the ligamentum arteriosum, whereas the right recurrent laryngeal nerve hooks around the right subclavian artery. All other nerves are not closely associated with the aortic arch.

40. Tha answer is C. (Pericardium and Heart: 11.E.l &2) The SA and AV nodes are in the wall of the right atrium and are not associated with the apex of the heart. The oblique cardiac vein drains into the coronary sinus, and the pulmonary veins empty into the left atrium. The right ventricle is hypertrophied by the pulmonary stenosis.

41. The answer is C. (Pericardium and Heart: 11.B.3.b & c.4) The chordae tendineae are tendinous strands that extend from the papillary muscles to the cusps of the valve. The papillary muscles and chordae tendineae prevent the cusps from being everted into the atrium during ventricular contraction.

42. The answer is C. (Pericardium and Heart: rv.c, Clinical Correlates, Transposition of the Great Vessels) A patent ductus arteriosus shunts blood from the pulmonary trunk to the aorta, partially bypassing the lungs, and thus allowing mixed blood to reach the body tissues and causing cyanosis. Dextroposition or transposition of the great arteries must be accompanied by a VSD or a patent ductus arteriosus for the infant to survive. The transposition causes oxygenated blood to pass from the left ventricle into the pulmonary trunk and then into the lungs, but deoxygenated blood travels from the right ventricle into the aorta and then into the systemic circulation.

43. The answer is C. (Mediastinum, Pleura, and Organs of Respiration: IX.A) The tracheoesophageal septum is formed by the fusion of the tracheoesophageal folds in the midline. This septum di· vides the foregut into a ventral portion, the laryngotracheal tube (primordium of the larynx, trachea, bronchi, and lungs), and a dorsal portion (primordium of the oropharynx and esophagus).

44. The answer is A. (Thoracic Wall: V.A) The intercostal veins, arteries, and nerves run in the costal groove beneath the inferior border of the ribs between the internal and the innermost layers of muscles. The transversus thoracis muscles are situated in the internal surface of the lower anterior thoracic wall.

45. The answer is D. (Pericardium and Heart: V.B) The left sixth aortic arch is responsible for the development of both the ductus arteriosus and the pulmonary arteries. The ductus arteriosus closes functionally in an infant soon after birth, with anatomic closure requiring several weeks.

46. The answer is B. (Mediastinum, Pleura, and Organs of Respiration: IX.B) Bronchial cartilages, smooth muscles, and connective tissue are derived from the mesoderm. The bronchial epithelium and glands are derived from the endoderm.

47. Tha answer is C. (Structures in the Posterior Mediastinum: II.A, Clinical Correlates, Figure 3.18) Stenosis of the ascending aorta results in left ventricular hypertrophy.

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BRS Gross Anatomy

48. The answer is B. (Mediastinum, Pleura, and Organs of Respiration: 11.B) During surgical treatment for cancer in the apex of the right lung by a lo bectomy, the right superior secondary (eparterial) bronchus should be removed.

49. The answer is E. (Mediastinum, Pleura, and Organs of Respiration: VII.CJ The right and left bronchial arteries arise from the descending (thoracic) aorta.

50. The answer is A. (Structures in the Posterior Mediastinum: 11.B.4, Figure 3.19) The azygos vein drains venous blood into the SVC.

51. The answer is C. (Pericardium and Heart: 11.F.l & 2) The right and left coronary arteries arise from the ascending aorta.

52. The answer is D. (Mediastinum, Pleura, and Organs of Respiration: II.CJ The left primary bronchus is crossed superiorly by the arch of the aorta and the pulmonary artery.

53. The answer is B. (Mediastinum, Pleura, and Organs of Respiration: II, Figure3.3) The right inferior lobar bronchus may be removed in a surgical resection of the inferior lobe of the right lung that is in contact with the diaphragm.

54. The answer is C. (Pericardium and Heart: IY.C, Clinical Correlates) Pulmonarystenosis results in right ventricular hypertrophy.

55. The answer is E. (Mediastinum, Pleura, and Organs of Respiration: VII.BJ The left atrium receives oxygenated blood from the lung by way of the pulmonary veins.

56. The answer is A. (Figure 3. 7) The SVC lies on the right side of the ascending aorta and the arch of the aorta.

57. The answer is C. (Figure 3.12) The right ventricle contains the septomarginal trabecula. 58. The answer is D. (Figure 3.12) The ascending aorta takes its origin from the left ventricle and ends at the level of the sternal angle by becoming the arch of the aorta.

Abdomen

ANTERIOR ABDOMINAL WALL I. ABDOMEN (Figure 4.1) • The abdominal cavity is divided into either four quadrants or nine regions to localize pain and/or describe the location of intra-abdominal organs. • Is most frequently divided by vertical and horizontal planes through the umbilicus into four topographic quadrants: right and left upper quadrants and right and left lawar quadrants. The umbilicus lies at the level of the lntervertebral disk between the third and fourth lumbar vertebrae. Its region is innervated by the 10th thoracic nerve. The nine-region system is topographically delineated by two transverse and two longitudinal planes. The named regions are the right and left hypochondriac, epigastric, right and left lumbar, umbilical, right and left inguinal (iliac), and the hypogastric (pubic) region.

CLINICAL CORRELATES

Umbilical llarnia is e protrusion of intestines through the umbilical ring and is covered by skin. It is often more noticeable when the infant cries or strains. It is not usually treated surgically because a majority close spontaneously by 3 years of age. Omphalacele is due to malrcrtation and failure of the mid gut to return to the abdomen in fetal life. The herniation of intestines is covered only by the thin amniotic membrane and peritoneum; thus, immediate surgical repair is required. Gastroschisis is a protrusion of abdominal viscera through a full-thickness abdominal wall defect and also requires surgical repair. Epigastric

Left hypochondriac

Transtubercular plane--'--+-.:,...::0:." --"""""'--'-'-1--...l....\,Right iliac---__.

Left iliac Hypogastrtc (suprapublc)

RGUREU. Planas af subdivision af the abdomen.

Right mid-Inguinal

Left mid-Inguinal

line

line

109

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BRS Graa Allatamy

II. MUSCLES OF THE ANTERIOR ABDOMINAL WALL (see Table 4.1)

Ill. FASCIAE AND LIGAMENTS OF THE ANTERIOR ABDOMINAL WALL • The superficial fascia of the abdominal wall is located between the skin and muscles of the ante· rior abdominal wall. It is composed of two layers, a s11p1rficial fatty layer (Camper) and a deeper membranous layer (Scarpa). A thin layer ofadipose tissue lies between the superficial fascia layers and the abdominal wall muscles.

A. Superficial fascia of Iha anterior abdominal wall 1. Superficial (fatty) layer of Iha superficial fascia • Is continuous with the superficlal fascia of the thigh. • Continues over the pubis and perineum as the superficial perinea! fascia.

2. Deap (m1mbrano11sl layer of the superficial fascia • Is attached to the fascia lata just below the inguinal ligament. • In the mid.line, it fuses with the linea alba and pubic symphysis.

• Continues over the penis as the superficial fascia and over the scrotum as the dartos tunic, which contains smooth muscle. Becomes continuous with the superficial fascia of the perineum {Colles fascia). In the female, it continues into the labia majora. • May contain extravasated urine and/or blood between this fascia and the deep fascia of the abdomen resulting from rupture of the spongy urethra.

B. Deep fascia • Covers the abdominal muscles and continues over the spermatic cord at the superficial inguinal ring as the IXlarnal sparmatic fascia.

C. Uneaalba • Is a tendinous median raphe between the two rectus abdoml.nis muscles, formed by the fusion of the aponeuroses of the external oblique, internal oblique, and transverse abdominal muscles. • Emmds from thexiphoid process to the pubic symphysis, and, in pregnancy, it becomes a pigmented vertical line (linaa nigra), probably as a result of honnone stimulation to produce more melanin.

t

a bIa

4.1

Muscles of the Anterior Abdominal Wall

Muscle

Origin

Insertion

NllVe

External oblique

Extemel surface of lower eight riba(S-121

Internal oblique

Llltllral two-thirds of inguinal ligament; iliac era st; 1hor11columbar flscia

Anterior half of iliac crest,; anterior superior iliac spine; pubic tubercle; linaa alba Lowar four costal cartilages; linaa alba; pubic crast; pectinaal line

Transvem abdominis

Lateral one-third of inguinal ligament; iliac crest; 1h11r1.011lumbar fascia; lower six costal ca rtila gas Pubic crest and pubic symphysis Pubic body

Xiph11id process and comI c1rlilagas fifth to s111111nth Linea alba

lntarcostal IT7-Tl1I; Compresses subcostal IT12) abdomen; fleos trunk; active in fore ad axpiration lntercostal IT7-TI 1); Compresses subcostal IT121; abdomen; flaxas iliohypogastric and trunk; active in forced ilioin guinal (L1I expiration lntarcostal IT7-Tl2); Compresses subcostal IT12I; abdomen; depresses iliohypogarbic and ribs ilioin guinal (l1) lntere 1151:81 IT7-TI 1); Depresses ribs; flexes subcostal IT121 trunk Subcoml IT12I Tensas lin11 alba

Pubic tubercle and crest

GanitvfamoraI

Rectus abdominis Pyramidal Cremaltlr

Middle of inguinal ligament lower margin of inmm1I 11bliqua muscla

Linea aIba; pubic crest pectinaal line

Action

Rvtrac:ts tastis

l.31tJ"rn Abdomen

111

CUNICAL

Epigastric hernia is a re re protrusion of small intestine through e weakness in the linee alba above the umbilicus. The hernia typically contains extraparitoneal fat or a small piece at graater omentum.

CORRELATES

D. Linea 11milunari1 Is a curved line along the lateral border of the rectus abdominis muscle.

E. Arcuata line (linea 11micirculari1) Is a crescent-shaped line marking the Inferior limit of the posterior layer of the rectus sheath just below the level of the Wac crest

F. Lacunar ligament (Gimbemat ligament) Represents the medial triangular expansion of the inguinal ligament to the pectineal line of the pubis. Forms the medial border of the femoral ring and the floor of the inguinal canal.

G. Pectinaal (Cooper) ligament Is a strong fibrous band that extends laterally &om 1he lacunar ligament along the pectineal line

of the pubis. H. Inguinal ligament (Poupart ligament) Is the folded lower border of the aponeurosis of the eictemal oblique muscle that extends from the anterior superior Wac spine to the pubic tubercle. Forms the Door (inferior wall) of the inguinal canal.

I. lliopectineal arcu1 or ligament Is a f11cial partition that separates the muscular (lateral) and vascular (medial) lacunae deep to the inguinal ligament. 1. The muscular lacuna transmits the iliopsoas muscle. 2. The vascular lacuna transmits the femoral sheath and its contents, including the femoral

veasels, a femoral branch of the genltofemoral nerve, and the femoral canal J. Rtrflectad inguinal ligament Is formed by fibers derived from the medial portion of the inguinal ligament and lacunar ligament and runs upward over the confoint tendon to end at the linea alba.

K. Faix inguinalis (conjoint tendon) Is formed by the aponeuroses of the internal oblique and transverse abdominis muscles and inserts into the pubic tubercle and crest. Strengthens the posterior wall of the medial half of the inguinal canal.

L. Rectus sheath (Figure 4.2) Is formed by fusion of the aponeuroses of the external oblique, Internal oblique, and transverse abdominls muscles of the abdomen. Encloses the rectus abdomlnls and the pyramidal muscle (if present). Also contains the superior and Inferior eplgastrlcvessels and the ventral primary raml ofthoracic nerves 7to12. 1. Anterior layer of 1ht rectus sheadl (a) Above the arcuate line. Aponeuroses of the external and internal oblique muscles. (b) Below the arcuate line. Aponeuroses of the external oblique, intemal oblique, and transverse abdominis muscles. 2. Posterior layer of 111• rectus sheath (a) Allo'we the 1rcu1t1 line.Aponeuroses ofdie internal oblique and transverse abdominis muscles. (b) Below the arcuate line. The posterior rectus shea1h is absent, and the rectus abdominis is In contact with 1he transversalls fascia.

112

BRS Graa Allatamy Rectus abdominis musde

Skin

External abdominal oblique muscle Transvarsalis fascia

Internal abdominal oblique muscle

Transverse abdomlnal muscle

Umblllcal prewsical fascia

RGURE 4.2. Arrangamant of 1ha ractus sha;ith 1bova the umbilicus ftopJ ind below 'Iha arculte line (bottom).

IV. INGUINAL REGION A. Inguinal (HBSSalbach) triangle • Is bounded medially by the llnea semilunarls (lateral edge of the recb.ls abdominis), laterallyby

the inferior epigastrlc vessels, and inferiorly by the inguinal ligament • A direct inguinal hamie protrudes through the abdominal wall through the inguinal triangle, medial to the inferior epigastrlc vessels.

B. Inguinal rings 1. Superficial inguinal ring • Is a triangular opening in the aponeurosis ofthe external oblique muscle that Ii.es just lateral to the pubic tubercle.

2. D11p inguinal ring • Is an opening in the transversalis fascia, just lateral to the inferior epigastric vessels.

C. Inguinal canal • Begins at the deep inguinal ring and terminates at the superfi.clal ring. • Transmits the spermattc cord or the round ligament of the uterus and the genital branch of the genitofemoral nerve, both of which run through the daap inguinal ring and the inguinal canal. An indirect inguinal hernia (if present) passes through this canal. Although the Uioinguinal nerve runs through part of the inguinal canal and the superficial inguinal ring, it does not pass through the deep inguinal ring. 1. Anterior wall. Aponeurosls ofthe external oblique muscle and is reinforced laterally byfibers of the internal oblique muscle. 2. Posterior wall. Aponeurosis ofthe transverse abdominal muscle and transversalis fascia and is reinforced medially by the conjoint tendon (fused fascias of the transverse abdominis and internal oblique muscles). 3. Suparior wall (roof). Arching fibers of the internal oblique and transverse muscles. 4. Inferior wall (floor). Inguinal and lacunar ligaments.

l:3lJtttl1I Abdomen

113

Extraperltoneal dssue

Internal obllque muscle Ex1ernal obllque muscle Coverings {Internal spermatlc fascia of the cord Cremaster muscle ---.J..l!Jll.7'~~~

External spennallc fascl

RGURE 4.1. A:. Cova rings of sparmetic cord and tllstis. B: Inguinal tiami11.

CLINICAL CORRELATES

Inguinal hernia arises when e portion of intestine protrudes through a weak spot in the inguinal canal or in the inguinal triangle. Inguinal hernia occurs superior to the inguinal ligament and lateral to the pubic tubercle and occurs mare in males than in females. Reducible hernia is a hernia in which the contents of the hernial sac can be returned to their normal position. Incarcerated hernia is an irreducible hemia in which the contents of the hernial sac are entrapped or stuck in the groin. Strangulatad harnia is an irreducible hernia in which the intestine becomes tightly trapped or twisted, compromising circulation, which can lead to gangrene (death of tissue) unless repair is prompt This is life-threatening; thus, emergency surgical repair is required. Indirect inguinal hernia passes through the deep inguinal ring, inguinal canal, and superficial inguinal ring and descends into the scrotum. Indirect hernias lie lateral to the inferior epigastric vessels, are congenital {present at birth), derived from persistence of the processus vaginalis, and covered by peritoneum and the coverings of the spermatic cord (Figure 4.3). Direct inguinal hernia occurs in the inguinal triangle directly through the abdominal wall muscles (posterior wall of the inguinal canal), lateral to the edge of the conjoint tendon (faIx inguinalis), and rarely descends into the scrotum. The hernia occurs medial to the inferiorapigalb'ic vessels and protrudes forward {but rarely through) the superficial inguinal ring. It is acquired {develops after birth) and has a sac formed by peritoneum and, occasionally, transversalis fascia.

V. SPERMATIC CORD, SCROTUM. AND TESTIS A. Spannatic cord (Figure 4.3) • Is composed of the ductus defarans; tmticular, crema.steric, and deferentialarteries; pampiniform plexus oftasticular nins; genital branch af th& ganitaftlmoral, cremasteric nerves, and the tesdcular sympathetic plexus; and lymph vessels. These are all interconnected by loose connective tissue.

BRS Graa Allatamy

114

• Has several fasclae:

1. External spermatic fascia, derived from the aponeurosis of the external oblique muscle. 2. Cremasteric fascia (cremastermuscle and fascia), originating from the internal oblique muscle. 3. lnt1mal 1p1nnatic fascia, derived from the transversalls fascia.

B. Fetal structures 1. Pracnsus vaginalis testis Is aperitoneal div1rtic11lum in the fetus that evaginates into the developing scrotum and forms the visceral and parietal layers of the tunica vaginalis testis. • Normallycloses before birth orshortlythereafterandloses its connection with the peritoneal cavity. • May accumulate fluid lhydrocele proc111u1 vaginalis) if it is patent. • May result in a congenital indirect inguinal hernia if it persists.

2. Tunica vaginalis • Is a double serous membrane, a peritoneal sac that covers the front and sides of the testis and 1pididymi1. • Is derived from the abdominal peritoneum and forms the innannost layer of the scrotum. 1 Gubernai:ulum testis • Is the fltal ligament that connects the bottom of the fetal testis to the developing scrotum. • Is important in testicular descant (pulls the testis down into the scrotum). Is homologous to the ovarian ligament and the round ligament of the uterus.

C. Scrotum • Consists of a thin pigmented skin and dartDS fascia, a layer ofsmooth muscle fibers; when contracted, it wrinkles for testicular temperature regulation. • Is innervated by the genital branch of the genitofemoral, anterior scrotal branch of the ilioinguinal, posterior scrotal branch of the perineal, and perineal branch of the posterior femoral cutaneous nerves. • Receives blood from anterior scrotal branches of the external pudendal artery and posterior scrotal branches of the internal pudendal artery • 4'Jnph from the scrotum drains into the superficial inguinal nodes.

D. Tastes • Are swrounded by the tunica vaginalis in the scrotum. • Produces spermin the seminiferous tubules and interstitial cells (ofLeyclig} produce testosterone. • Are innervated by autonomic nerves, receive blood from the testicular arteries arising from the aorta, and drain venous blood via testicular veins, which empty into the inferior vena cava (IVC) on the right and the renal vein on the left. • Lymphatic drainage follows the testicular arteries into the lumbar (aortic) nodes.

VI. INNER SURFACE OF THE ANTERIOR ABDOMINAL WALL (Figure 4.4) A. Umbilical folds or ligaments 1. Median umbilical ligament or fold • Is a fibrous cordlike remnant of the obliterated urachus covered by peritonewn. • Lles between the t:ransversalis fascia and the peritoneum and extends from the apex of the bladder to the umbilicus.

2. Medial umbilical ligament or fold • Is a fibrous cordlike remnant of the oblitaratad umbilical artery covered by peritoneum and extends from the side of the bladder to the umbilicus.

3. Lateral umbilical fold • Is a fold ofperitoneum that covers the inferior epigastricvessels and extends from the medial side of the deep inguinal ring to the arcuate line.

B. Supravasical fossa • Is a depression on the anterior abdominal wall between the median and medial umbilical folds of the peritoneum.

l:3lJtttl1I Abdomen

115

.:l'.IF=--,..._~---.llf.r.:....--Round

ligament of liver and paraumbilical vein

Medial umbilical fold Median umblllcal fold--~~-~~r-+fl~A.:.i. Femoral nerw--.....:,,~~·1 External iliac V88891s----l~~~'~

.

.:~-- Ductus defarans

~~;

.-:-

~"ii----

Obturator nerw and vessels

Seminal vesicle

Prostate RGURE 4.4. Umbilical folds over the antllrior abdominal wall.

C. Madial inguinal Iona • Is a depression on the anterior abdominal wall between the medial and lateral umbilical folds of the peritoneum. It lies lateral to the supravesical fossa. • Is the fossa where most direct inguinal hemiu occur.

D. Lataral inguinal fo111 • Is a depression on the anterior abdominal wall, lateral to the lateral umbilical fold of the peritoneum.

E. Transver1ali1 fascia • Is the lining fascia ofthe entire abdominopelvic cavity between the parietBI peritoneum. and the Inner surface of the abdominal muscles. • Is continuous with the diaphragmatic, psoas, iliac, pelvic, and quadratu.s lwnborum fasciae. • Forms the daap inguinal ring and gives rise to the femoral sheath and the Internal spermatlc fascia. • Is directlyin contact with the posterior rectus sheath above and with the rectos abdominis muscle below the arcuate line.

VII. NERVES OF THE ANTERIOR ABDOMINAL WALL A. Subcostal nerve • Is the ventral ram.us of the 12th thoracic nerve and innervates muscles of the anterior abdominal wall. • Has a lateral cutaneous branch that innervates skin on the side of the hip.

11&

BRS Graa Allatamy

B. lliahypagallric narve • Arises from the first lumbar nerve and Innervates the internal oblique and transverse abdomlnis muscles of the abdomen. • Divides into a lateral cutaneous branch to supply skin on the lateral side of the buttocks and an anterior cutaneous branch to supply skin above the pubis.

C. llioinguinal narva • Arises from the first lumbar nerve, pierces the internal oblique muscle near the deep inguinal ring, and accompanies the spermatic cord through the inguinal canal and then through the superficial inguinal ring. • hmervates the internal oblique and transverse abdominis muscles. • Gives rise to a famoral branch, which innervates the upper and medial parts of the anterior thigh, and the anterior scrotal nerve, which Innervates the skin of the root of the penis (or the skin of the moos pubis) and the anterior part of the scrotum {or the labium majus).

CLINICAL CORRELATES

Cramaslaric raft ax is a drawing up of Iha testis by contraction of the eremaster muscle when the skin on the upper medial side of the thigh is stroked. The ef· ferent limb of the reflex arc is the ganital branch of tha ganilafamoral narva; the afferent limb is the femoral branch of Iha genitolamoral nerve and the ilioinguinal nerve.

VIII. LYMPHATIC DRAINAGE OF THE ANTERIOR ABDOMINAL WALL A. Lymphatics in the rag ion above the umbilicus • Drain into the axillary lymph nodes.

B. Lymphatics in the region below the umbilicus • Drain into the superficial inguinal nodes.

C. Superficial inguinal lymph nodes • Receive lymph from the lower abdominal wall, buttocks, penis, scrotum, labium majora, and the distal parts of the vagina and anal canal. Their efferent vessels primarily enter the external iliac nodes and ultimately drain to the lumbar (aortic) nodes.

IX. BLOOD VESSELS OF THE ANTERIOR ABDOMINAL WALL A. Superior apigastric artery • Arises from the internal thoracic artery, enters the rectu.s sheath, and descends on the posterior surface of the rectus abdominis. • Anastomoses with the inferior epigastric artery within the rectus abdominis.

B. Inferior epigastric artery • Arises from the external iliac artery above the inguinal ligament and ascends between the rectus abdominis and the posterior layer of the rectus sheath. • Anastomoses with the superior epigastric artery, providing collateral circulation between the subclavian and external iliac arteries. • Givea rise to the cramasteric artery, which accompanies the spermatic cord.

C. Daap circumflex iliac artery • Arises from the external iliac artery and runs laterally along the inguinal ligament and the iliac crest between the transverse and internal oblique muscles. • Forms an ascending branch that anastomoses with the musculophrenic artery.

l:3lJtttl1I Abdomen

117

D. Superficial epigastric arteries • Arise from the femoral artery and run superiorly toward the umbilicus over the inguinal ligament. • Anastomosewith branches of the inferior epigastric artery.

E. Sup1rficial circumflex iliac artery • Arises from the femoral artery and runs laterally upward, parallel to the inguinal ligament. • Anastnmose.s with the deep clrcumtlex iliac and lateral femoral circumflex arteries.

F. Superficial (external) pudendal arteries • Arise from the femoral artery, pierce the crtbriform fascia, and run medially to supply the skin above the pubis.

G. lboracoapigastric veins • Are longitudinal venous connections between the lateral thoracic vein and the superficial epigastric vein. • Provide a collateral route fur venous return if a caval or portal obstruction occurs.

PERITONEUM AND PERITONEAL CAVllY I. PERITONEUM • ls a seraus membrane lined by mesothellal cells. • Consists of the parietal paritonaum and the viscaral peritoneum.

A. Parielal paritonaum • Lines the abdominal and pelvic walls and the inferior swface of the diaphragm. • Is innervated bysa•tic nerves, such as the phreoic, lower intercostal, subcostal, iliohypogastric, and ilioinguinal nerves.

B. Viscaral paritonaum • Covers the viscera, is innervated by visceral nerves, and is insensitive to pain.

II. PERITONEAL REFLECTIONS (Figure 4.5) • Support the viscera and provide pathwayll fur associated neurovascular structures.

A. Omentum •

Is a fold of peritoneum extending from the stomach to adjacent abdominal organs.

1. Lesser omentum • • • • •

Is derived from the embryonic ventral m.esen.tery. ls a double layer of peritoneum extending from the porta hepatis of the liver to the lesser curvature of the stomach and the beginning ofthe duodenum. Consists ofthe hapatogastric and hapatoduodanal ligamenll and forms the anterior wall of the lesser sac of the peritoneal cavity. Transmits the left and right gastric vessels, which run between its two layers along the lesser curvature of the stomach. Contains the proper hapatic artary, bile duel, and portal vain within its right free margin.

2. Greetar omantum • •

•

ls derived from the embryonic dorsal me.sentery. Hangs down like an apron from the greater curvature ofthe stomach, covering the transverse colon and other abdommal viscera. Can preventloops ofsmall intestine from passing into a herniated sac by pluggingthe entrance.

BRS Graa Allatamy

118

Liver

.Jlf!"":.~-. ~!g-......._.J..if--+f--Bare area of liver \-ti....,~+----ir+-Superior

recess

Epiploic (omental) furamen ~1-J.1-1-J>.!-"--=-;1~q..,""' --+-111o=H-----tf--Lesser sac Jl'"---+-A:.~f--ff- Lesser omentum

Stomach -11'--frl+---li,,,_ Greater sac: - - - -

Greater omentum

Sigmoid colon

Sigmoid mesocolon

RGU RE 4.5. S111itt11I sa ction of the abdoman.

•

Transmits the right and left gastroepiploicvessels along the greater curvature. Wraps and

•

is an Inflammation of the peritoneum characterized by an accumulation of peritoneal fluid that contains fibrin and leukocytes (pus). Has the following subdivisions:

adheres around inflamed abdominal organs, thus preventing diffuse peritonitis. Peritonitis

(al Gastrolienal (gastro1plenic) ligament Extends from the greater curvature ofthe stomach to the hilum ofthe spleen and contains the short gastric and left gastraapiploic vessels.

(bl Lienarenal (1plenarenal) ligament Runs from the bilum oftb.e spleen to the left kidney and contains the splenic vessels and the tail of the pancreas.

(cl Gastraphrenic ligament •

Runs from the upper part ofthe greater cu.rvarure ofthe stomach to the diaphragm.

(di Gastrocolic ligament Runs from the greater curvature of the stomach to the transverse colon.

B. M11enteri11 1. Menntery of the small intestina (mesantery proper) • Is a fan-shaped double fold of paritonaum that suspends the jejunum and the ileum from the posterior abdominal wall and transmits nerves and blood vessels to and from the small intestine. • Forms a root that mewls from the duodenojejunal flexure to the right iliac fossa and is approximately 15 cm (6 in,) long. • Has a free border that encloses the small intaltina, which is apprmdmately 6 m (20 ft) long. • Contains the superior mesenteric and intestinal ijejunal andlleal) vessels, nerves, and lymphatics.

2. Transverse masocolon • Connects the posterior surface of the transvern colon to the posterior abdominal wall. • Puses with the greater omentum to form the gastrocolic ligament. Contains the middle colic vessels, nerves, and lymphatics.

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119

3. Sigmoid mesocolon

• Connects the sigmoid colon to the pelvic wall and contains the sigmoid vessels. Its line of attachment may form an inverted V. 4. Mesaappendix Connects the appendix to the mesentery of the ileum and contains the appendicularvessels.

C. Othar paritonaal ligamants 1. Phrtnicocolic ligament • Rnns from the left colic Oexure to the diaphragm.. Z. Falcifonn ligament Is a sickle-shaped peritoneal fold connecting the liver to the diaphragm and the anterior abdominal wall. • Contains the ligamenlUm tires hepatis and the paraumbilical vein, which connects the left branch of the portal vein with the subcutaneous veins in the region of the umbilicus. • Is derived from the embryonic ventral mesentery. 3. Ligam1ntum tires h1pati1 (round ligament of the liver) Liel inthe free maigin ofthe falclform ligament and aacendi from the umbilicus to the inferior (visceral) surface of the ~ lying in the fissure that forms the left boundary of the quad.rate lobe of the liver. • Is a remnant of the laft umbilical vain, which carrlea oxygenated blood from the placenta to the left branch of the portal vein in the fetus. (The right umbilical vein is obliterated during the embryonic period) 4. Coronary ligament • Is a peritoneal reOection from the diaphragmatic surface of the liver onto the diaphragm and encloses a triangular area of the right lobe, the bare area of Iha liver. • Has right and left extensions that form the right and laft triangular ligaments. 5. Ligam1nt11m venosum • Is the fibrous remnant of the duct111 venosus. Lles in the fissure on the inferior surface of the liver, forming the left boundary ofthe caudatl lobe of Iha liver.

D. Paritonnl folds 1. Rectouterine fold Extends from the cervix ofthe uterus, along the &Ide ofthe rectum, to the posterior pelvic wall, forming the rectouterine pouch (of Douglas). Z. lleocecal fold • Extends from the terminal ileum to the cecum.

Ill. PERITONEAL CAVITY (see Figure 4.5) ls a potential space between the parietal and visceral layers of peritoneum and contains a film of fluid that lubricates the surface of the peritoneum and facilitates free movements of the viscera. • Is a completely closed sac in the male but is open in the female through the uterine tubes, uterus, and vagina. It is divided into the lesser and greater sacs.

CLINICAL CORRELATfS

Peritonitis is an inflammation and/or infection of the peritoneum. Common causes include leakage of fa cal material from a burst appendix, a penetrating wound to the abdomen, a perforating ulcer that leaks stomach contents into the peritoneal cavity (lesser sac), or poor sterile technique during abdominal surgery. Peritonitis can be treated by rinsing the peritoneum with large amounts of sterile saline solution and giving antibiotics. Paracentesis (abdominal tap) is a procedure in which a needle is inserted 1to2 in. through the abdominal well into the peritoneal cavity to obtain e sample or drain fluid while the patient is sitting upright The entry site is midline at approximately 2 cm below the umbilicus or lateral to Mc Burney point,. avoiding the inferior epigestric vessels.

12D

BRS Graa Allatamy

A. Lasser sac (omental bursa) • Is an irregular space that lies behind the liver, lesser omentum, stomach, and upper anterior part of the greater omentum. • Is a closed sac, except for its communication with the greater sac through the epiploic (omenllO

foraman (of Winslow). • Presents three recesses: (a) 1uparior rac111, which lies behind the stomach, lesser omentum, and left.lobe of the liver; (b) inlarior recess, which lies behind the stomach, extending into the layers of the greater omentum; and (c) splenic rec111, which extends to the left at the hilum of the spleen.

B. Greater sac • Extends across the entire breadth of the abdomen and from the diaphragm to the pelvic Door and presents numerous recesses.

1. Subphranic (suprahapatic) recess •

Is a peritoneal pocket between the diaphragm and the anterior and superior part of the liver and ls separated into right and left recesses by the falcifann ligament

2. Subhapatic recess or hapatorenal recess (Morrison pouch) •

Is a deep peritoneal pocket between the liver anteriorly and the kidney and suprarenal gland posteriorly and communicates with the right paracollc gutter (and thus the pelvic cavity) and the lesser sac via the epiploic forameo.

3. Paracolic recesses (gutters) •

Ue lateral to both the ascending colon (right paracollc gutter) and the descending colon (left paracolic gutter).

C. Epiploic or omantal (Winslow) foreman • Is a natural opening between the lesser and greater sacs. • Is bounded superiorly by the caudate lobe ofthe liver, inferiorly by the first part of the duodenum, anteriorly by the free edge of the lesser omantum, and posteriorly by the IVC.

GASTROINTESTINAL (GI) VISCERA I. ESOPHAGUS (ABDOMINAL PORTION) • Is a muscular tube (appromnately 10 in. or 25 cm long) that extends from the pharynx to the stomach. The short abdominal part (1/2 in, long) extends from the diaphragm to the cardiac orifice of the stomach, entering the abdomen through an opening in the right crus of the diaphragm. This distal portion is located in the epigastric region of the abdomen. • The upper esophageal sphincter is the crtcopharyngeus part orthe inferior pharyngeal constrictor. • The physiologic lower 11ophag11I sphincter is a circular layer of smooth muscle at the terminal portion of the esophagus. The tonic contraction of this sphincter prevents the stomach contents from regurgitating into the esophagus. In addition, the diaphragmatic musculature forming the esophageal hiatus functions as a physiologic external esophageal sphincter.

CLINICAL CORRELATfS

Gastroesophageal reflux disease is caused by lower esophageal sphincter dysfunction (relaxation or weakness) and/or hiatal hernia, ca using reflux of stomach contents. This reflux disease has symptoms of heartburn or acid indigestion, painful swallowing, burping, and a feeling of fullness in the chest. It can be treated surgically by moving the herniated area of stomach back into the abdominal cavity and tightening ttle esophageal hiatus. Hiatel or esophageal hernia is herniation of the stomach through the esophageal hiatus into the thoracic cavity. The hernia is caused by an abnormally large esophageal hiatus in the diaphragm, a relaxed and weakened lower esophageal sphincter, and increased pressure in lhe abdomen resulting from coughing, vomiting, straining, constipation, or pregnancy. It may cause gastroasophageal reflux, strangulation of the esophagus or stomach, or vomiting in an infant after feeding. Treatment of a symptomatic hernia includes managing gastroesophageal reflux andlor surgery to repairthe hernia (fundoplication).

l!1iO'ml

Abdomen

121

II. STOMACH (Figures 4.6 to 4.8) Its posterior surface lies in the shallow stomach bed, which is formed by the pancreas, spleen, left kidney, left suprarenal gland, transverse mesocolon, and diaphragm. The potential space of the lesser sac separates the stomach bed from the posterior surface of the stomach. Is covered entirely by peritoneum and is located in the left upper quadrant of the abdomen. • Has greater and l11nr curvature1, cardiac and pyloric openings, and cardiac and angular notches. Is divided into four regions; cardia, fund us, body, and pylorus. The fundus Iles inferior to the apex of the heart. The pylorus is divided into the pyloric antrum and pyloric canal. The pyloric orifice is surrounded by the pyloric sphinctar, which Is a group of thiclcened circular smooth muscles that

Cardiac part Cardiac notch

Lesser curvature Angular notch

Spleen

Duodenum Biie duct·---1....._-+o,-'--i

Main pancreadc duct

,,....--Graeter curvature 7-:>6"'~~:::._Suspensory ligament (ofTreitz) Duodenojejunal flexure

Superior meaenterlc artery Head of pancreas

Superior mesenterlc vein

RGURE 4.li. Stomach and duodenum.

Superior (first) part of duodenum '-.,.

Body

of stomach

Descending (second) part ot duodenum

Horizontal (third)

part of duodenum RGURE U. Radiograph of 1h11 stnm11ch and small intBstinH.

122

IRS Gross Anatomy auadrate lobe ......... o!IM!r

Ligamentum

teres hepatls smmach Hepatic artery

C.udate IObe ct liver =~;--Aorta

Spleen Diaphragm

Gallbladder

Portal vein Inferior vena c:ava

Deacanding colOn

Rlghtcrus diaphragm

Aorta Spleen

•wTranlMllr'll& colOn Superior mesenterlc artery

Left kidney Ileum

Deecending colOn

ln!arfor van a CIMl

Renal pyramid

Peou ma;or muade

Aorta Ileum Sigmoid colon -.~-

Left common lllacartery

Right psoas

muec:re FIGURE 4.8. Campllted tomography scans of the abdomen 1t different levels.

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123

control the rate of discharge of stomach contents into the duodenum. The sphincter is constricted by sympathetic stimulation and relaxed by parasympathetic action. • Receives blood from the right and left gastric, right and left gastroepiploic, and shortgastric arteries. • The internal surface of the body and fundm has rugae, longitudinal folds of mucOUB membrane. Within the lesser curvature, the mucosa Is smoother, forming the gastric canal that directs fluids toward the pylorus. • Produces mucus, hydrochloric acid, pepsin, and the hormone gastrin. Mucus protects the stomach from self-digestion. Hydrochloric acid destroys many organisms and provides the required acidic environment for pepsin activity, which breaks down proteins into polypeptides. Gastrin stimulates gastric acid secretion. Parasympathetic fibers of the vagus nerve also stimulate gastric secretion.

CLINICAL CORRELATES

Peptic ulcer is erosion in the lining of the stomach or duodenum. It is commonly caused by an infection with Helitoblt:ttt pylori bacteria or regular use of nonsteroidal anti-inflammatories. It occurs most commonly in the pyloric region of the stomach (gastric ulcer) or the first part of the duodenum (duodenal ulcer). Symptoms of peptic ulcer are epigastric pain (burning, cramping, or aching), abdominal indigestion, nausea, vomiting, loss of appetite, weight loss, end fatigue. It may be treated with antibiotics or surgical intervention, including a partial gastrectomy and vegotomy. Gastric ulcers may perforate into the lesser sac and erode the pancreas and the splenic artery, causing fetal hemorrhage. Duodanal ulcers are three times more common then gastric ulcers and may erode the pancreas er the gastroduodenal artery, causing burning, cramping, and epigastric pain.

Ill. SMALL INTESTINE (see Figures 4.6 to 4.8) • Extends from the pyloric opening to the lleocecal junction. • Is the location ofcompl11:9 digestion and absorption ofmost ofthe products ofdigestion, electrolytes, and minerals, such as calcium and iron. • Consists of the duodenum, jejunum, and ileum.

A. Duodenum • Is a C-shaped tube surrounding the head ofthe pancreas and is the shortest (25 cm (10 in.] long) and widest part of the small intestine. • Is retroperitoneal except for the first part, which is connected to the liver by the hapatoduodanal

ligament of the lesser omentum. •

Receives blood from the celiac {furegut) and superior mesenteric {midgut) arteries.

• Is divided into four parts: 1. Superior (first) pad: • Has a mobile or free section, termed the duodenal cap (because of its appearance on radiographs), into whlch the pylorus invaglnates. 2. Dascanding lsecondl part • The junction of the foregut and midgut lies jUBt below the major duodenal papilla where the common bile and main pancreatic ducts open. • The minor duodenal papilla, which lies 2 cm above the major papilla, marks the site of entry of the accessory pancreatic duct 3. Tranm1rse (third) part • Is the longest part and crosses the IVC, aorta, and vertebral column from right to left. • Is crossed anteriorly by the superior mesenteric vessels. 4. Ascending (fourth) part • Ascends to the left of the aorta to the level of the second lumbar vertebra and terminate& at the duodenojejunal junction, which is fixed in position by the suspensory ligamant (of Traitz). This fibromuscular band is attached to the right crus of the diaphragm.

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CLINICAL CORRELATES

Small bowel obstruction is caused by postoperative adhesions, tumors, Crohn disease, hernias, peritonitis, gallstones, volvulus, congenital malrotation, stricture, and intussusception (invagination of one part of the intestine into another). Strangulated obstructions are surgical emergencies and may cause death if untreated due to arterial occlusion which leads to bowel ischemia and necrosis. Symptoms include colicky abdominal pain and cramping, nausea and vomiting, constipation, dizziness, abdominal distention, and high-pitched bowel sounds. Inflammatory bowel disease includes Crohn disease and ulcerative colitis. Crohn disease usually occurs in the ileum (ileitis or enteritis), but it may occur in any part of the digestive tract Symptoms include diarrhea, rectal bleeding, anemia, weight loss, and fever. Ulcerative colitis involves the colon and the rectum, causing ulcers in the lining (mucosa) of the organs, and patients with prolonged ulcerative colitis are at increased risk for developing colon cancer. Celiac disease is an immune reaction tD eating glutan (protein of wheat, barley, and rye). Gluten ingestion triggers an immune system response resulting in inflammation that damages Iha lining of the small intHlina, causing malabsorption of nutrients, constipation, diarrhea, vitamin and mineral deficiencies, fatigue, and weight loss. B. Jejunum • Lies between the duodenum and the ileum. • Is emptier, larger in die.meter, and thicker walled than the ileum. • Has plicaa circulares (circular folds), whlch are tall and closely packed. • Has trlllllllucent areas called windDWI between the blood vessels of its mesentery. • Has less prominentartarial arcades (anastomoticloops) in its mesentery compared with the ileum. • Has longer vasa recta (straight arteries, or arterlae rectae) compared with the ileum. C. llaum • Is longer than the jejunum and occupies the iliac fossa in the right lower quadrant • Is characterized by the presence of Peyer patches (aggregations of lymphoid tissue), shorter pllcae clrculares and vasa recta, and more mesenterl.c fat and arterial arcades when compared with the jejunum. • The ileocecal fold (bloodless fold of Treves named after a surgeon at the London Hospital who drained the appendicular abscess of King Edward VII in 1902) is a peritoneal fold located between the ileum and the cecum.

CLINICAL CORRELATES

Meckel diverticulum is a fingerlike outpouching of the ileum, derived from an unobliterated vitelline duct, and is located Zft proximal to the ileocecal junction on the antimeunteric side. It is approximately 2 in. long, occurs in approximately 2% of the population, may contain two types of ectopic tissues {gastric and pancreatic), presents in the first two dacadas of life and more often in the first 2 years, and is found two tim11 as frequently in boys as in girls. It represents persistent portions of the embryonic yolk stalk (vitelline or omphalomesenteric duct) and may be free or connected to the umbilicus via a fibrous cord or a fistula. The diverticulum may cause diverticulitis, ulceration, bleeding, perforation, bowel obstruction, abdominal pain and discomfort, vomiting, fever, and constipation.

IV. LARGE INTESTINE (see Figures 4.8 and 4.14) • Extends from the ileocecal junction to the anus and is apprmimately 1.5 m (5 ft) long. • Consists of the cacum, appendix, colon, rectum, and anal canal. • Functions to convert the liquid contents ofthe ileum into semisolid feces by absorbing water, salts, and alactrolytas. It also stores and lubricates feces with muCUB.

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125

A. Colon Has ascending and dascanding colons that are retroperitoneal and tnn1V1rs1 and sigmoid colons that are surrowtded by peritoneum. (the tran1Y1rse mnocolon and the sigmoid masocolon, respectively). The ascending and transverse colons are supplied by the superior mesenteric artery and the vagus nerve proximal to the left colic (splenic) flexure; the descending and sigmoid colons are BUpplied by the inferior mesenteric artery and the pelvic splanchnic nerves. Is characterized by the following: 1. Teniae coli. Three narrow bands of the outer longitudinal muscular coat 2. Sacculations or haustn. Produced by the teniae, which are slightly shorter than the gut tube. 3. Epiploic appendages. Peritoneum-covered sacs offat, attached in rows alongtheteniae coli.

CUNICAL

Diverticulitis is an inflammation of diverticula (external evaginations) of the intestine I wall, commonly found in the colon, especially the sigmoid colon, and the diverticul1 develop as a result of high pressure within the colon. Symptoms are abdominal pain usually in the left lower abdomen (but can be anywhere), chills, fever, nausea, and constipation. Risk factors include older age and a low-fiber diet, and diverticulitis can be treated with rest. high-fiber diet, and antibiotics. Complications may include bleeding, perforations, peritonitis, and stricture or fistula formation. Sigmoid volvulus is a twisting of the sigmoid colon around its mesentery, creating a colonic ob· struction and may cause intestinal ischemia that may progress to infarction and necrosis, peritonitis, and abdominal distension. It may occur when the sigmoid colon and its mesantary are abnormally long. Symptoms include vomiting, abdominal pain, constipation, bloody diarrhea, and hamatemasis. Megacolon (Hi11chsprung disease) is caused by the absence af enteric ganglia (call bodies of parasympathetic postganglionic fibers) in the lower part of the colon, leading to dilation of the colon proximal to the inactive segment It is of congenital origin, results from failure of neural crest cells to migrate and form the myenteric plexus, and is usually diagnosed during infancy and childhood. Symptoms are constipation or diarrhea, abdominal distention, vomiting, and a lack of appetite. Colostomy is the most effective treatment the surgeon removes the affected pa rt of the colon, and the proximal part of the colon is then connected to a surgically created hole, called a stoma, on the abdomen. After the lower part of the colon heals, the surgeon reconnects the colon inside the body and closes the stoma.

CORRELATES

B. Cecum Is the blind tnd pouch of1he luge intestine. Itlies in the right iliac fossa and is usually sunounded by peritoneum but has no mesentery. C. Appendix Is a narrow, hollow, muscular tube with large aggregations of lymphoid tissue in its wall. Is suspended &om the terminal ileum by a small mesentery, the mnoappendix, which contains the appendicular vessels. causes spasm and distention when inftamed, resulting in pain thatls referred to the perlumbilical region and movea down and to the right. Has a base that lies deep to McBurney point, which occuu at the Jwtction of the lateral one-third ofan imaglnuy line between the right anterior superior iliac spine and the umbilicus. This is the site of maxlmwn tenderness in acute appendicitis.

CUNICAL

Acute appendicitis is an acute inflammation of the appendix. usually resulting from bacteria or viruses that are trapped by fecal obstruction of the lumen. Symptoms include rebound tenderness, perium bilical pain that may move to the right iliac fossa on Mc Burney point, accompanied by loss of appetite, nausea, vomiting, fever, diarrhea, and consti· pation. Its rupture may cause peritonitis, leading rapidly to sapticemia and eventually daath, if untrHtad. Appendicitis can be treated by appendectomy.

CORRELATES

12&

BRS Grass Anatomy

D. Rectum and anal canal • Extend from the sigmoid colon to the anus. Are described as pelvic organs (see Pelvis: vm, Chapter 5).

CLINICAL CORRELATES

Colonoscopy is an internal examination of the colon, using a flexible colonoscope with a small camera. The colon must be completely empty, the patient lies on his or her side, and the colonoscope is inserted through the anus and gently advanced to the terminal small intestine. Because better views are obtained during withdrawal than during insertion, a careful examination is done during withdrawal of the scope, looking for bleeding, ulcers, diverticulitis, polyps, colon cancer, end inflammatory bowel diseases. Tissue biopsy may be taken.

V. ACCESSORY ORGANS OF THE DIGESTIVE SYSTEM A. Liver (Figures 4.8 and 4.9) • Is the larglll: visceral organ and the largest gland in the human body. Plays an hnportant role in production and secretion af bile (used in emulsification of fats); detoxification (by filtering the blood to remove bacteria and foreign particles that have gained Medial superior area

Anterlor------superlor area

--1--Lateral superior area

Posterior---superior area

Posterlor---1

inferior area Anterior _ __ inferior area

Ligamentum teres hepatis --(left umbilical vein)

- - - Medial inferior area (IV), quadrate lobe

- - Falclfonn ligament

Posterior lnfertor area (VI)

Caudate process

Posterior superior --11~-­

111--- -+-UgamenlUm venosum

area (VII)

- - - --Ir-

Lateral superior

area (II)

Inferior vena cava

RGURE 4.9. Antario r 1nd vis caral surface ofIha liver and divisians of th a Iivar basad on hap1tic dr1ina 11a and blood supply.

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127

entrance from the intestine); storage of carbohydrate as glycogen (to be broken down later to glucose); production and storage ofllplds as triglycerid11; plasma protein synth11i1 (albumin and globulin}; production of blood coagulants (flbrinogen and prothrombin), anticoagulants (heparin), and bile pigments (bWrubin and biliverdin) from the breakdown of hemoglobin; reserwoir for blood and platelets; and storage of certain vitamins, iron, and coppei:. In the fetus, the liver is important in the manufacture of red blood cells. Is surrounded by the peritoneum. and is attached to the diaphragm by the coronaFJ, falcif'onn, and the right and left triangular ligaments. Has a bare area devoid ofperitoneum on the diaphragmatic surface, which is limited by layers of the coronary ligament. Receives oxygenated blood &om the hepatic lrtll'J and deoxygenated, nutrient-rich blood from the portal vein; its venous blood is drained by the hepatic veins Into the IVC. Contains internal. portal 1riads, which are branches of the portal vain, hepatic art•FJ, and bile duct at every comer of a liver lobule. Is divided, based on hepatic drainage and blood supply, into the right and ltrft lob11 by the fossae for the gallbladder and the NC. (These lobes correspond to the functional units or hepatic segments.) 1. Lobes of the liver (see Figure 4.9) The right and left lobes are separated byfussae for the gallbladder and the NC. Liver lobes are further divided into eightfunctionally independentsegments (Couinaud, 1957). Bach segment can be identified numerically or by name. (a) The Right Lobe is divided into anterior and posterior segments, each of which is subdivided into superior and inferior areas or segments. (b) The Left Lobe is divided into medial and lateral segments, each ofwhich is subdivided into superior and inferior areas (segments). (c) The Quadrat& Lobe receives blood from the left hepatic artery and drains bile into the left hepatic duct lt is descrfbed as being part ofthe right lobe, butls functionally related to the left lobe. (d) The Caudate Lobe receives blood from the right and left hepatic arteries and drains bile into both right and left hepatic ducts. It is descrlhed as being part of the right lobe, but is functionally distinct from both the right and left lobes of the liver. 2. FiRurM and ligaments of the liwer (see Figure 4.9) The fissures and ligaments are arranged in an H shape: (a) Fissure for the round ligament (ligamentum ten. hepatis), located between the lateral portion of the left lobe and the quadrate lobe. (b) Fissure for the ligamentum vanosum, located between the caudate lobe and the lateral portion of the left lobe. (c) Fossa for the gallbladder, located between the quadrate lobe and the major part of the right lobe. (d) Fi&rure for the IVC, located between the caudate lobe and the major part of the right lobe. (e) Porta hepatis is the1ransverse fissure on the visceral surface of the liverbetween the quadrate and caudate lobes. It contains the hepatic ducts, hepatic arteries, branches of the portal vein, hepatic nerves, and lymphatic vessels.

CUNICAL

liver cinhosis is a condition in which liver cells are progressively destroyed and replaced by fatty and fibrous tissue that surrounds the intrahepatic blood vessels and biliary radicals, impeding the circulation of blood through the liver. It is caused by chronic alcohol abuse (alcoholism). viral hepatitis, and ingestion of poisons. Liver cirrhosis causes portal hypertension, resulting in esophageal varices (dilated veins in the lower part of the esoph· agus), hamonhoids (dilated veins around the anal canal), caput m1du11 (dilated veins around the umbilicus), spider nevi or spider angioma {small, red, spidertike arterioles in the cheeks, neck, and shoulder), ucites (accumulation of fluid in the peritoneal cavity), 1d1m1 in the legs (lower albumin levels facilitate water retention), iaundice (yellow eyes or skin resulting from bile duct disease failing

CORRELATES

1211

BRS Graa Allatamy

to remove bilirubinl. hepatic encephalopathy (shunted

blood bypassing the liver contains toxins that reach the brain), 1pl1nom1galy (enlarged spleen resulting from venous congestion causing sequestered blood cells that lead to thrombocytopania, a low platelet count and easy bruising), hapatomegaly (due ta fatty changes and fibrosis), palmar erythema (persistent redness of the palms), testicular atrophy, gynacomastia, and pectoral alopacia (loss of hair). Liver biopsy is perfonned percutaneously by needle puncture, which commonly goes through the right 8th or 9th (perhaps 7th to 10th) intercostal spa ca in the right midaxillary line under ultrasound or computed tomography scan guidance. While taking the biopsy, the patient is asked to hold his or her breath in full expiration to reduce the costodiaphragmatic recess and to lessen the possibility of damaging the lung and causing pneumothorax. Transjugular liver biopsy is also accomplished by inserting a catheter into the right internal jugular vein and guiding it through the superior vane cave, IVC, and right hepatic vein. A biopsy needle is inserted through a catheter into the liver where a biopsy sample is obtained.

B. Gallbladder (see Figures 4.8 to 4.10) • Is a pear-shaped sac located in a fossa between the right and quadrate liver lobes with a capacity ofapproximately 30 to 50 mL. It is also in contact with the duodenum and tranSYerse colon. • Consists of the fundus, body, and neck: the fundua is the rounded blind end located in the midclavicular line and contacts the transverse colon; the body is the major part and rests on the upper part ofthe duodenum and the transverse colon; the nack is the narrow part and gives rise to the cystic duct with spiral valv11 (Heister valves). • Receives bile, concentrates it (by absorbing water and salts), stores it, and releases it during digestion. • Contracts to expel bile as a result of stimulation by the hormone cholacptokinin, which is produced by the duodenal mucosa or by parasympathetic stimulation when food arrives in

the duodenum. • Receives blood from the cystic artery, which typically arises from the right hepatic artery within thecyatollepatic triangle !of Calot), which is formed by the visceral surface ofthe liver superiorly, the cystic duct inferiorly, and the common hepatic duct medially.

Left hepatic duct

Llver--4'-:r.---Gallbladder: Fundus ---r.r!I+-- -...

Body--\ff!------1 Neck----li1 - - - -

Accessory pancreatic duct and lesser duodenal papilla

Hepatopancreatic ampulla RGURE 4.10. Exlrahapatic bile p111a11ea and pancreatic ducts.

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129

CUNICAL

Galls1ann (cholalilhs or cholelitlli11i1) are formed by solidification of bile constituents and composed chiefly of chala118ral crystals, usually mixed with bile pigments and calcium. Bile crystallizes and forms sand, gravel, and finally stones. Gallstones present commonly in fat. fertile (multiparousl females who are older than forty (40) years (4-F individuals). Stones may become lodged in the (a) fundus of tile gallbladder, where they may ulcerate through the wall of the fund us of the gallbladder into the transverse colon or through the wall of the body of the gallbladder into the duodenum (in the fonner case, they are passed naturally to the rectum, but in the latter case, they may be held up at the iltoctcal iunction, producing an intestinal ollslruction); (b) bile duct. where they obstruct bile flow to the duodenum, leading to i1u1dic1; and (c) h1p1top11creatic ampulle, where they block both the biliary and the pancreatic duct systems. In this case, bile may enter the pancreatic duct system, causing aseptic or noninfectious pancreatitis.

CORRELATES

CUNICAL

Cholecystitis is an inflammation of the gallbladder caused by obstruction of the cystic duct by gallstones. It causes pain in the upper right quadrant and the epigastric region, fever, nausea, and vomiting. The pain may radiate to the back or right shoulder region. Cholacystactomv is open or laparoscopic surgical removal of the gallbladder necessitated by inflammation or the presence of gallstones in the gallbladder.

CORRELATES

C. Pancre11 (see Figures 4.8 and 4.10) lles largely in the floor of the lesser sac where it forms a major portion of the stomach bed. Is a retroperitoneal organ except for a small portion of its tail, which lies in the litnorenal (splenorenal) ligament. Has a head that Iles within the C-shaped concavity of the duodenum. If tumors are present in the head, bile flow can be obstructed, resulting in iaundice. JaWldice occurs when bile pigments (bll!rubin) accumulate In the blood, giving the skin and eyes a yellow tinge. The uncinate process ls a projection ofthe Inferior part of the head that extends medially behlnd the superior mesenteric vessels. The uncinated process is formed from the ventral pancreatic bud during development. The neck connects the head and body of the pancreas and lies anterior to the junction of the superior mesenteric and splenic veins, forming the hepatic portal vein. The body mends from the neck to the tail and is the longest part of the pancreas. The tail projects toward the hilum. of the spleen. Receives blood from branches of the splenic artery and &om the superior and inferior pancreatlcoduodenal arteries. Is both an exocrine gland, which produces digestive enzymes Involved in digestion of fats, proteins, and carbohydrates, and an endocrine gland (Islets of Langerhans), which secretes the hormones Insulin, glucagon, and somatostatln. Insulin lowers blood sugar levels by stimulating glucose uptake, glycogen formation, and storage. Glucagon elevates blood sugar levels by promoting conversion of glycogen to glucose. Somatostatin suppresses insulin and glucagon seaetion. Has two ducts, the main p1ncr11tic duct and the acc911ory pancreatic ductwhich carry exocrine pancreatic secretions.

1. Main pancreatic duct(duct of Winung) Begins in the tail and nms to the right along the entire pancreas. Joins the bile duct to form the hepatopancreatic 1mpulla (1mpulla of Yater) before entering the second part of the duodenum at the greater papilla.

2. Accessory pancreatic duct (Santorini duct) Begins in the inferior portion of the head and drains a small portion of the head and body. Empties at the minor Oesser) duodenal papilla appronmately 2 cm above the greater papilla.

130

BRS Graa Allatamy

CLINICAL CORRELATES

Pancrutiti1 is an inflammation of the pancreas caused by gallstones or alcohol abuse. Symptoms include upper abdominal pain (which may be severe and constant and may present as back pain), nausea, vomiting, weight loss, fatty stools, mild jaundice, diabetes, low blood pressure, heart failure, and kidney failure. Pancreatic cancer frequently causes severe back pain, has the potential to invade into the adjacent organs, and is extremely difficult to treat Cancer of the pancreatic head often compresses and obstructs the bile duct. usually causing a painless obstructive jaundice. Surgical resection called a pancreaticoduodenectomy (Whipple procedure) can be curative in this particular instance. Cancer of the pancreatic neck and body may cause portal or IVC obstruction because the pancreas overlies these large veins.

CLINICAL Diabetes mellitus is characterized by hyperglycemia that is caused by an inCORRELATES adequate production of insulin or in1d1quat1 action of insulin on body tissues. There are two types of diabetes: type I diabetes (also known as insulin-dependent diabetes), in which P-cells of the pancreas produce an in1uflici1nt amount of insulin; and type II diabetes, which results from insulin resistance of target tissues (a condition in which the body fails to properly use insulin or fails to respond properly to the insulin action, typically as a result of obesity). Unless properly managed, diabetes will lead to diabetic retinopathy, neuropathy, kidney failure, heart disease, stroke, and limb disease. It has symptoms of polyuria (excessive secretion of urine), polydipsia (thirst}, weight loss, tiredness, infections of urinary tract. and blurring of vision.

D. Duct system for bile passage (see Figure 4.10)

1. Right and left hepatic ducts • Are formed by union of the intrahepatic ductules from each lobe of the liver and drain bile from their corresponding halves of the liver. 2. Common hepatic duct • Is formed by union of the right and left hepatic ducts. • Is accompanied by the proper hepatic artery and the portal vein. 1 Cystic duct • Has spiral folds (valves) to keep it constantly open, and thus bile can pass upward into the gallbladder when the common bile duct is closed. Joins the common hepatic duct to fonn the common bile duct. Is a common site ofgallstone impaction. 4. Common bile duct lductua chol1dochu1) • Is formed by union of the common hepatic duct and the cystic duct. • Is located lateral to the proper hepatic artery and anterior to the portal vein in the free margin of the lesser omentum. • Descends behind the first part ofthe duodenum and runs through the head of the pancreas. Joins the main pancreatic duct to form the hapatopancreatic duct(hapatopancreatic ampulla), which enters the second part of the duodenum at the major (greater) duodenal papilla. • The bile duct sphincter ls a circular muscle layer a.round the lower end of the duct 5. Hapatopancreatic duct or ampulla (ampulla of Yater) • Is formed by the wlion of the common bile and main pancreatic ducts. The sphincter of Oddi is a circular smooth muscle layer around the ampulla of the major duodenal papilla.

VI. SPLEEN (see Figures 4.6, 4.8, and 4.12) • Is a large vascular

lymphatic organ lying against the diaphragm and ribs 9 to 11 in the left hypochondriac region, covered by peritoneum except at the hilum, and supported by the lianogastric lsplenagastric) and lienorenal lsplenorenal) ligaments.

l!ilIJ't!l1I Abdomen

131

It is supplied by the splenic artery and drained by the splenic vein. Is composed of white pulp, which consists ofprimarily lymphatic tissue around the central arteries and is the primary site of immune and phagocytic action, and red pulp, which consists of venous sinusoids and splenic cords and is the primary site offiltration. Filtan blood (macrophages remove damaged and worn-out erythrocytes and platelets); acts as a blood reservoir, storing blood and platelets in the red pulp; participates in the immune response

(protection against infection); and produces mature lymphocytes, macrophages, and antibodias chiefly in the white pulp. Is hamatopoiatic in early life and later destroys aged (i.e., worn-out) red blood cells in the red pulp and releases hemoglobin from the spent RBCs. Hemoglobin, a respiratory protein of erythrocytes, is degraded into (a) glob in (protein part), which is hydrolyzed to amino acids and reused in protein synthesis; (b} iron released from the heme, which is transported to the bone marrow and reused in eryth.ropoiesis; and (c) iron-free heme, which is metabolized to bllirubin in the liver and excreted in bile.

CLINICAL

Splenomegaly is caused by venous congestion resulting from thrombosis of the

CORRELATES splanic vain or portal hypertension, which causes sequestering of blood calls, leading ta thrombocytopenia (a low platelet count} and easy bruising. It has symptoms of fever, diar-

rhea, bone pain, weight loss, and night sweats. Ruptura of Iha splaan occurs frequently by fractured ribs or severe blows to the left hypochondrium and causes profuse bleeding. The ruptured spleen is difficult to repair; consequently, splanactumy is performed to prevent the person from bleeding ta death. The spleen may be removed surgically with minimal effect on body function bee a use its functions are assumed by other retie ulo· endothelial organs. Lymphoma is e cancer of lymphoid tissue. Hodgkin lymphoma is a malignancy characterized by painless, progressive enlargement of the lymph nodes, spleen, and other lymphoid tissue, accompanied by night sweats, fever (Pel-Ebstein fever), and weight loss.

VII. DEVELOPMENT OF DIGESTIVE SYSTEM (Figure 4.11) A. Primitive gut tube • Is a hollow tube lined by endoderm that is covered by splanchnic m.esoderm. It is derived from the yolk sac during craniocaudel and lateral folding of the embryo. The endoderm forms the epithelial lining and glands of the gut tube mucosa, whereas the splanchnic mesodenn forms all other layers (smooth muscle and submucosa). • During development, it opens to the yolk sac through the vitelline duct that divides the embryonic gut into the foregut, midgut, and hindgut B. Foragul 1. Foregut derivatives Are supplied by the celiac artery. 2. Esophagus Develops from the narrow part of the foregut that is divided into the esophagus and trachea by the tracheoesophageal septum. 3. Stomach Devel.ops as a fusiform dilation of the foregut during week 4. The primitive stomach rotates 90 degrees clock.wise during development, resulting in formation of the lesser peritoneal sac and the greater omentum (dorsal mesentery of the stomach). 4. Duodenum Develops from the distal end of the foregut (upper duodenum) and the proximal segment of the mldgut Oower duodenum). The junction of the foregut and midgut is at the opening of the common bile duct

132.

BRS Grass Anatomy

Ven

-Stomach

m~

Dorsal mesentery

=oregut artery celiac artery)

'ancreas

gut artery Jertor mesenterlc artery) artery

Cle

meeenterlc artery) umu1111;a1 aruny

RBURU.11. Formation Dfthe midgut loop and the fnregut. midgut, and hindgut arteries. (Reprinted with permission from Lllngman J. Medical Embl'fO/agy. 4th ed. Baltimore, MD: Williams&. Wilkins: 1981:150.)

5. Liver • Develops as an endodermal outgrowth ofthe foregut. the hepatic diverticulwn, and ls involved in hematopoiesis from week 6 and begins bile formation in week 12. • Liver parenchym.al cells and the lining of the biliary ducts are endodermal derivatives of the hepatic diverticulum.

(a) Hepatic dinrticulum • •

Grows into the mass ofsplanchnic mesoderm called the septum transversum. Proliferates to form the liver parenchyma. Sends hepatic cell cords to surround the vitelline veins, which form hepatic sinusoids.

(b) Septum transvenum Is a mesoderrnal mass located between the developing pericardial and peritoneal cavities after embryonic folding. Gives rise to Kupffer cells and hematopoietic cells, as well as the central tendon of the diaphragm. 6. Gallbladder Develops from the hepatic diverticulum as a solid outgrowth of cells. The end ofthe outgrowth expands to form the gallbladder, and the narrow portion forms the cystic duct The connection betweeD the hepatic diverticulum and foregut narrows to form the bile duct

1. Pancreas • Arises as ventral and dorsal pancreatic buds from endoderm of the caudal foregut The ventral bud rotates posteriorly with rotation of the duodenum to fuse with the dorsal bud. • The ventral pancreatic bud forms the uncinate process and partofthe head ofthe pancreas, and the dorsal pancreatic bud forms the remaining part ofthe head, body, and tail ofthe pancreas. • The main pancreatic duct is formed by fusion of the duct of the ventral bud with the dlstal part of the duct of the dorsal bud. The accessory pancreatic duct is formed from the proximal part of the duct of the dorsal bud.

CLINICAL

CORRElATES

Annular pancreas occurs when the ventral and dorsal pancreatic buds form a

ring around the duodenum, dlereby obstructing it

8. Spl11n • Develops as a proliferation ofmesenchym.e in the dorsal mesogastrium in week 5 and hematopoietic organ until week 15. Although it is not an embryologic derivative of the foregut. it is considered with the foregut because it receives the same blood supply and innervation as other foregut structures.

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133

C. Midgut 1. Midgut derivatives • Are supplied bythe superiormesenteric artery.

Z. Lawer duodenum Arises from the upper portion of the midgut 1 The midgut loop • Is formed by rapid lengthening of the gut tube, communicates with the yolk sac by way of the vitelline duct or yolk stalk. and herniates through the umbilicus during the physiologic umbilical herniation. Rotates 270 degrees counterclockwise around the superior me&mteric artery as it returns to the abdominal cavity. la) The cranlal limb of the mi.dgut loop forms the jejunum and ileum (cranlal portion). lb) The caudal limb forms the caudal portion of the ileum, cecum, appendix, ascending colon, and the tranSY1rse colon (proximal two-thirds).

D. Hindgut 1. Hindgut derivatives are supplied by the inferior mesenteric artery. 2. Cranial and of the hindgut forms the transverse (distal third), descending. and sigmoid colons. 1 Caudal end of the hindgut joins the allantois (diverticulum of the yolk sac into the connecting stalk) and forms the cloaca. The dilated cloaca is divided by the uroractal septum into the rectum and anal canal dorsally and the urogenital sinus ventrally, which forms the urinary bladder.

CLINICAL CORRELATES

Anorectal agenesis occurs when the rectum ends as a blind sac above the puborectalis muscle, whereas anal agenesis occurs when the anal canal ends as a blind sac owing to abnormal fonnation of the uroractal septum.

E. Proctodeum • Is an invagination of the ectoderm of the terminal part of the hindgut, which gives rise to the lower anal canal and the urogenital external orifice.

F. Masentarias • The primitive gut tube is suspended within the peritoneal cavity of the embryo by the ventral and dorsal mesenteries, from which all adult meaenteries are derived. • Ventral m111ntary forms the lesser omentum, falciform, coronary, and triangular ligaments. • Dorsal mesentery forms the greater omentum, the mesentery of the small intestine, mesoappend.Ix. transverse mesocolon, and sigmoid mesocolon.

VIII. CELIAC AND MESENTERIC ARTERIES A. Caliac trunk (Figures 4.12 and 4.13) • Arises anteriorly from of the abdominal aorta Immediately below the aortic hiatus of the diaphragm, between the right and left crura. • Divides into the left gastric, splenic, and common hepatic arteries. 1. Left gastric artery • Is the smallest branch of the celiac trunk. • Runs upward and to the left toward the cardia. giving rise to esophageal and hepatic branchas and then turns to run along the lesser curvature ofthe stomach within the lesser omentum to anastomose with the right gastric artery.

2. Splenic artery • Is the largest branch of the cellac trunk and runs a highly tortuous course along the superior border of the pancreas and enters the lienorenal ligament.

134

IRS Gross Anatomy

Left gastroepiploic

Right gastroepiploic

FIGURE 4.U. Branches oftha caliac trunk. Celiac 1runk

Left gastric artery

•----·Js:i

Left hepatic artery Right hepatic

Splenic

artery

Left

Proper hepatic artery Gastroduodenal

gastroeplplolc

artery

artery

artery

Superior pancreaticoduodenal artery

Catheter

Right gastroepiploic artery

FIGURE 4..13. Celiac angiogram showing its three major branches. {Reprinted with permission from Agur AMR, Darley AF. Grant'$ AtJIJI ofAnatomy. 12th ad. Philadelphia, PA: Lippincott Williams & Wilkins; 2C09:131.)

Gives rise to the following:

(a) AnUDlber of pancreatic branches, including the dorul pancreatic artery. (b) A few short gastric arteries, which pass through the lienogastric ligament to reach 1he fundu.s of1he stomach. (c) The left gastroepiploic (gastro-omental) artery, which reaches the greater omentum through the lienogastrlc ligament and runs along the greater curvature of the stomach to supply the stomach and greater omentum.

3. Cammon hepatic artery Runs to the right along the upper border of the pancreas and gives rise to the proper hepattc artery, the gastroduodenal artery, and, occu!.onally, the right gastric artery.

l.31tJ"rn Abdomen

135

(a) Praper hepatic artery Ascends In the free edge of the lesser omentum and divides, near the porta hepatis, into 1he left and right hepatic arteries. The right hepatic artery typically gives rise to the cystic artery in the cystohepatic triangle af Calat (bounded bythe common hepatic duct, cystic duct, and inferior surface of the liver). Gives rise promnally to the right gastric artery (most common origin of the right gastric).

CUNICAL

Pringle maneuver is a temporary cross-clamping (intermittent soft vascular CORRELATES clamping) afthe hepatoduodenal ligament containing portal triads at the foremen of Winslow for control of hepatic bleeding during liver surgery or donor hepatectomy for living donor liver transplantation.

(b) Right gastric artery Arises from the proper hepatic or common hepatic artery, runs to the pylorus and along the lesser curvature of the stomach, and anastomoses with the left gastric artery.

(c) Gestroduodenal artery Descends behind 1he first part of the duodenum, giving off the supraduodenal artery to its superior aspect and a few retroduodenal arteries to its inf'erior aspect. Divides into two major branches: 1. The right gastroepiploic (9astro·om1ntal) artery runs to the left along the greater curvature of the stomach, supplying the stomach and the greater omentum. 2. The superior pancreaticoduodenal artery passes between the duodenum and the head of the pancreas and further divides Into the anterlor-6Uperlor pancreaticoduodenal artery and the posterior-euperlorpancreaticoduodenal artery. B. Superior mesentaric artery (Figure 4.14) Arises anteriorly from the aorta behind the neck of1he pancreas. Descends across the undnate process of the pancreas and the third part of the duodenum and then enters the root of the mesentery behind the transverse colon to nm to the right iliac fossa. Gives rise to the following branches: 1. Inferior pancreaticoduodenal artery Passes to the right and divides into the anterior-inferior pancreaticoduodenal artery and the posterior-inferior pancreaticoduodenal artery, which anastomose with the c:orrespondlng branches of the superior pancreaticoduodenal artery.

2. Middle colic artery Enters the transverse mesocolon and divides Into the right branch, which anastomoses with the right colic artery, and the left branch, whlch anastomoses with the ascending branch ofthe left colic artery. The branches ofthe mesenterlc arteries form an anastomotic channel, 1he marginal artery, along the large intestine.

3. Right colic artery Arises from the BUperior mesenteric artery or the lleocolic artery. Runs to the right in the mesenteryand divides into uctnding and d11ctnding brtnch11, distnouting to the ascending colon.

4. lleocolic artery Descends in the mesentery toward the right iliac fossa and ends by dividing into the as· cending colic artery, which anastomoses with the right colic artery, anterior and posterior cecal arteries, the apptndicular artery, and iltal branches.

5. lnllstinal arterias Are 12to15 in nwnber and BUpplythe jejunwn and ileum. Branch and anastomose to form a series of arcades in the mesentery.

136

IRS Gross Anatomy Superior mesentertc artery

...-tt---H-+--++7"1-~Left

colic artery ~~-=~*--b4\:---+-

Inferior mesentertc artery

Ileum --+---A-'~_,.-++­ Antertor cecal artery ~~.,.....~!=ti.-~/

Epiploic (omental) · appendage

FIGURE 4.14. Branches of the auperior 1nd inl'erior meaenteric arteries.

CUNICAL

Superior mesentaric artery obstruction is caused by a thrombus, an em bolus, atherosclerosis, an aortic aneurysm, a tumor in the uncinate process of the pancreas, compression by the third pa rt of the duodenum, or surgical sear tissue. The obstruction leads to small and large intestinal ischemia, resulting in necrosis of all or part of the involved intestinal segment Symptoms are abdominal pain, nausea, vomiting, diarrhea, and electrolyte imbalance.

CORRELATES

C. Inferior m111nteric artery (see Figure 4.14) Passes to the left behind the peritonewn and distributes to the descending and sigmoid colons and the upper portion of the rectum. Gives rise to the following: 1. Left colic artery Runs to the left in the colic mesentery toward the descending colon and divides into 11cending and descending branchH.

2. Sigmoid arterits Ar.e two to three in number, run toward the sigmoid colon in its mesentery, and divide into ascending and descending branches. 3. Superior rtctal artery Is the termination of 1111 inferior m111nlaric artery, descends into the pelvis, divides into two branches that follow the sides of the rectum, and anastomoses with the middle and inferior rectal arteries. (The middle and inferior rectal arteries arise from the internal Wac and internal pudendal arteries, respectively.)

l3lJ'1CZJ Abdomen

137

IX. HEPATIC PORTAL VENOUS SYSTEM • Is a system of vessels in which blood collected from one capillary bed (of intestine) passes through the portal vein and then through a second capillary netwmk (liver sinusoids) before reaching the IVC (systemic circulation).

A. Portal Y9in (see Figures 4.8 and 4.15) • Drains the abdominal part of the gut, spleen, pancreas, and gallbladder. • Is formed bytheunion ofthesplenic vein and the superior masantaric vein posterior to the neck of the pancreas. The inferior mesenteric vein Joins either the splenic, the superior meaenteric vein, or the junction of these two veins. • Receives the left gastric (or coronary) vein. • Carries deoxygenated blood containing nutrients. • Carries three times as much blood as the hepatic artery and maintains a higher blood pressure than in the IVC.

Inferior vena cava

Aorta

Right branch of portal vein ~~5""""':>;3;:A._~~

Right gastric vein

---"'"""~--Inferior

mesenterlc vein

Inferior rectal vein RGURE 4.15. Portal venous system.

138

IRS Gross Anatomy Ascends posterior to the bile duct and hepatic artery within the free margin of the lesser omentum. 1. Superior mesenteric vein Accompanies the superior mesenteric artery on its right side in the root of the mesentery. Crosses the third part of the duodenum and the unclnate process of the pancreas and tennlnates posterior to the neck of the pancreas by jolnJng the splenlc vein, thereby forming the portal vein. Has trlbutarles that are veins that accompany the branches ofthe superior mesenterlc artery. 2. Splenic vein ls fonned by the union of tributaries from the spleen. Receives 1he short gastric, left gastroepiploic, and pancreatic veins. 3. Inferior mHenteric vein ls Conned by the union of the superior rectal and sigmoid veins. Receives 1he left colic vein and usually drains into the splenic vein, but it may drain into the superior mesenteric vein or the junction ofthe superior mesenteric and splenic veins. 4. Left gastric (coronary) vein Drains into 1he portal vein. Has esophageal tributarias that anastomose with the esophageal veins of the azygos system at the lower part of the eaophagus and thereby enter the systemic venous system. 5. Paraumbilical weins Are foWld 1n the falciform ligament and are virtually closed; however, they dilate in portal hypertension. Connect the left branch of the portal vein with the small subcutaneous veins in 1he region of the \UDbilicus, which are radicles of the superior epjgasttic, inferior epiga.stri.c, thoracoepigasttic, and superficial epigasttic veins.

CUNICAL

Portal hypertension results from liver cirrhosis or thrombosis in Iha portal vein, forming esophageal varices, caput medusae, and hemorrhoids. It can be treated by diverting blood from the portal to the ceval system by a partacenl shunt, achieved by surgically creating a communication between the portal vein and the IVC, as they lie close together below the liver, or by a splenorenal (Warren) shunt, accomplished by anastomosing the splenic vein to the left renal vein. Portal hypertension can also be treated bytransjugular intrahepatic portosystemic shunt in which a catheter is pis ced percutaneously into the right interns Ijugular vein through which an intrahepatic shunt is created between a hepatic vein and a branch of the portal vein within the liver, followed by placement of an expandable stent in the created tract or channel, and thus blood flows direcdy from the portal vein into the hepatic vein and then into IVC.

CORRELATES

B. Important portal-caval (systemic) anastomoses (see Figure 4.16) Anastomoses occur between these veins: 1. The left gastric vein and the esophageal vein ofthe azygos system. Clinical significance arises with portal hypertension, resulting in esophageal varlces. 2. The superior rectal vein and the middle and inferior rectal veins. Clinical significance with portal hypertension is rectal varlces. 3. The paraumbilicalveins and radicles of the epigastric (superficial and inferior) veins. Clinical significance with portal hypertension is caput medusa. 4. The retroperitoneal veins draining the colon and tributaries of the renal, suprarenal, and gonadal veins. This becomes clinically significant if a patient with varices undergoes a retroperitoneal surgical procedure. C. Hepatic veins Consist of the right, middle, and left hepatic veins that lle in the intersegmental planes and converge into the lVC on the superior surface of the liver. Have no valves, and the middle and left veins frequently unite before entering the vena cava.

l.31tJ"rn Abdomen

139

Azygos system

"C8put Medl.ISU"

Eaophageal and gutlic vattcea

Dilated retroparltoneal vein•

Inferior mesenteric vein tributaries -+__;_..~~-.r. Retroperltoneel veins

-----+-+....31-...,,

D Portal system D Inferior vena cava system (systemic cfrculatlon)

Q Associated clinical presentations

Rectal wrlcea (hemorrhoids)

SUperlor rectal veins ~~:9'~4---lnferfor and middle rectal veins

FIGURE 4.1&. Portal-i:aval anastomoses and associated clinical presentations.

CUNICAL CORRELATES

Budd-Chiari syndrome is an occluion af the hepatic veins and results in high

pressure in the veins, causing hepatomegaly, upper right abdominal pain, ascites, mild jaundice, and, eventually, portal hypertension and liver failure. It can be 1reated by balloon angioplasty or surgical bypass of the clotted hepatic vein into the vena cava or infusion of thrombolytics in to the blood vessel to break down clot.

140

BRS Graa Allatamy

RETROPERITONEAL VISCERA, DIAPHRAGM, AND POSTERIOR ABDOMINAL WALL I. KIDNEY, URETER. AND SUPRARENAL GLAND A. Kidney (see Figures 4.8 and 4.17) • Is retroperitoneal and extends from Tl2 to L3 vertebrae in the erect position. The right kidney lies a little lower than the left owing to the large size of the right lobe of the liver. The right kidney usually ls related to rib 12 posteriorly, whereas the left kidney is related torlbs 11 and 12 posteriorly. • Is invested by a firm, fibrous renal capsule and is surrounded by the renal fascia, which divides the fat into two regions. The perirenal (perinephric)fatlies in the perinephric space between the renal capsule and renal fascia, and the pararenal (paranaphric) fat lies external to the renal fascia. • Has an indentation (hilus) on its medial border, through which the ureter, renal vessels, and nerves enter or leave the organ. • Consists of the madulla and cDrtex, containing 1 to 2 million naphrans (in each kidney), whlcb are the anatomic and functional units of the kidney. Each nephron consists ofa renal corpuscle (found only in the cortex), a proximal convolutad tubula, renal loap (Df Hanle), and a distal canvoluted tubule. • Has arterial segments, including the superior, anterasuperiar, anterainferiar, inferior, and pasteriar 11gments, which are ofsurgical importance. • Filters blood to produce urine; reabsorbs nutrients; ucrate1 urine (by which metabolic or toxic waste products are eliminated) and foreign substances; ragulatas salt, ion (alactrolyta), and water balance; and produc11 erythropoietin. • Jwttaglomerular cells (in the wall of the afferent arterioles) produce renin. This hormone converts anglotensinogen (plasma protein from the liver) to anglotensin I (inactive decapeptide), whlch is then converted in the lungs by angiotensin-Converting enzyme to angiotensin II (potent vasoconstrictor). Angi.otensln II in.creases blood pressure and volume and stimulates aldosterone production by the suprarenal cortex, thereby regulating salt, ion, and water balance.

RGU RE 4.17. Fronte1aa ction of the kill ney.

l.31tJ"rn Abdomen

14t

t. Cortex Forms the outer part or the kidney and also projects into the medullary region between the renal pyramids as renal columns. Contains renal corpuscles and proximal and distal convoluted tubules. The re11I corp11cle consists of the glomerulus (a tuft or capillaries) surrounded by a glomerular (Bowman) capsule, which is the invaglnated blind end of the nephron. 2. Medulla Forms the inner part of the kidney and consists of 8 to 12 renal pyramid• (of Malpigbi}, which contain descending and ascending tubules (loops of Henle) and collecting tubules. The apex of a renal pyramid, the renal papilla, fits into the cup-shaped minor calyx on which the collecting tubules open (10-25 openings). 3. Calyc11 Minor calyca receive urine from the collecting tubules and empty Into two or three major calyca, which, in tum, empty Into an upper dilated portion or the ureter, the renal pelvis.

CUNICAL

Pelvic kidney is an ectopic kidney that occurs when kidneys fail to ascend and thus remain in the pelvis. Two pelvic kidneys may fuse to form a solid lobed organ because of fusion of the renal anlagen, called a cake (l'Olltla) kidney. Horseshoe kidney develops as a result of fusion of the lower poles of two kidneys and may ob· struct the urinary tract by its impingement on the ureters. Nephroptosit is downward displacement of the kidney, dropped kidney, or flNting kidney ca used by loss of supporting fat The kidney moves freely in the abdomen and even into the pelvis. It may cause a kink in the ureter or compression of the ureter by an aberrant inferior polar artery, resulting in hydronephrosis. Polycystic kidney disease is a genetic disorder charactarized by numerous cysts filled with fluid in the kidney. The cysts can slowly replace much of normal kidney tissues, reducing kidney function and leading to kidney failure. It is caused by a failure of the collecting tubules to join a distal convoluted tubule, which causes dilations ofthe loops of Henle, resulting in progressive renal dysfunction. This kidney disease has symptoms of high blood pressure, pain in the back and side, headaches, and blood in the urine. It may be treated by hemodialysis or peritoneal dialysis and kidney transplantation.

CORRELATES

CUNICAL

Kidney stone (renal calculus or nephrolidl) is formed by combination of a high level of calcium with oxalate, phosphate, urea, uric acid, and cystine. Crystals and sub seq uentty stones are formed in the urine and collected in calyees of the kidney or in the ureter. The kidney stone varies in size from a grain of sand to the size of a golf ball and produces severe colicky pain while traveling down through the ureter from the kidnayto the bladder. Common signs of kidney stones include nausea and vomiting, urinary frequency and urgency, and pain during urination.

CORRELATES

B. Ureter Is amuscular tube that begins wUh the renal pelvis, extending from the kidney to the urinary bladder. Is rettoperitoneal, where it descends on the transverse processes of the lumbar vertebrae and the psoas muscle, is crossed anteriorly by the gonadal vessels, and crosses the bifurcation of the

common iliac artery. May be obstructed by renal calc:uli (kidney stones) that tend to lodge at three anatomical constrictions; where it joins 1he renal pelvis (ureteropelvic junction), where it crosses the pelvic brim over the distal end of the common mac artery, or where it enters the wall of the urinary bladder (ureterovaicular junction). Receives blood from the aorta and renal, gonadal, common and internal iliac, umbilical, superior and inferior veslcal, and middle rectal arterlea. Is innervated by lwnbar (sympathetic) and pelvic (parasympathetic) splanchnlc nerves.

142

BRS Gross Anatomy

CLINICAL CORRELATES

Obstruction of the ureter occurs by renal calculi or kidney stones where the ureter joins the renal pelvis (ureteropelvic junction), where it crosses the pelvic brim, or where it enters the wall of the urinary bladder (ureterovesic ular junction). Kidney stones at these narrow points result in hydroureter and hydronephrosis. Hydronephrosia is a fhaid-filled 1nl1rg1m1nt of die renal pelvis and calycea as a result of obstruction of the ureter. It is due to an obstruction of urine flow by kidney stones in the ureter, by compression on the ureter by abnormal blood vessels, or by the developing fetus at the pelvic brim. It has symptoms of nausea and vomiting, urinary tract infection, fever, dysuria (painful or difficult urination), urinary frequency, and urinary urgency.

C. Supraranal (ad'9nal) gland (Figure 4.18) • Is a retroperitoneal organ lying on the superomedial aspect of the kidney. It is surrounded by a capsule and renal fascia. • Its shape is pyramidal on the right and semilunar on the left. • Has a cortex that is essential to life and produces three types of steroid hormones produced in different layers. These layers can be remembered through the use of the mnemonic MSEX;" 1. The outer zona glomerulosa produces mineralocorticoids, mainly aldosterone {"salt" steroids). Aldoaterone controls electrolyte (sodium, potassium. etc.) and water balance. 2. The middle zona fasclculata produces glucocorticoids, mainly cortisol and corticosterone (Manergy" steroids). Cortisol controls glucose regulation and suppresses immune response. 3. The inner zona reticularis produces androgens (Msex• steroids). Androgen is responsible for the development ofsecondary sex characteristics and libido in females. Has a medulla thatis derived from embryonic neural crest cells, receives preganglionic sympathetic nerve fibers directly, and secretes epinephrine and norepinephrine directly into the bloodstream. Receives arteries from three sources: the superior suprarenal artery from the inferior phrenic artery, the middle suprarenal artery from the abdominal IOrta, and the inferior suprarenal artery from the renal artery. Is drainedvia the suprarenal vein, which empties into the IVC on the right and the renal vein on the left. Middle suprarenal artery

Inferior phrenlc artery-+---;----'().

"-~--1----r Inferior phrenlc vain ,,__.,.___ _ _ _ Inferior phrenic artery

Supartor suprarenal---!!,.,__~----ll artery \\ Suprarenal gland---!-+---~

U-1™::-----Hlf-Superior suprarenal artery '-~~---+--Inferior suprarenal artery Suprarenal vein ----~-!---+---->!~J.--.~~~~~..J..!,.:.--';'ft-~r--Renal artery :~~~W'~7i7.1-/-Renel vein +-+----'f'!!----+---Tes!Scular vein ~-~~~~-Tes!Scular artery

Inferior mesenterlc artery

\ RGURE 4.18. Suprarenal glands, kidneys, and abdominal aorta and its branches.

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143

CUNICAL CORRELATES

Addison disease is a disorder caused by an adrenocortical insufficiency (insufficient production of cortisol and, in some cases, aldosterone) resulting from autoimmune destruction of the suprarenal cortex or tuberculosis. Symptoms include muscle weakness, loss of appetite, weight loss, fatigue, low blood pressure, darkening of the skin, nausea, vomiting, and diarrhea. Disorders of the supra renal cortex are caused by an excess production of hormones. Cush· ing syndrome results tram an excess af glucocorticoids and presents with trunk obesity, moon face, muscle weakness, high blood pressure, hyperglycemia, and kyphosis. Conn syndrome is caused by an excess af aldosterone, and its symptoms include hypertension, headache, muscle cramps, fatigue, polyuria, and polydipsia. An overproduction of androgens results in excess hair growth. The term hirsutism is used clinically to describe excess hair distributed in a male pattern in females.

II. DEVELOPMENT OF KIDNEY. URINARY BLADDER. AND SUPRARENAL GLAND • Kidney and suprarenal cortex develop from mesoderm., but suprarenal medulla develops from neural crest cells.

A. Kidney Devel.ops from intermediate mesoderm.. 1. The pronephros appears early, degenerates rapidly, and never forms functional nephrons. 2. The muanephros largelydegenerates but fonns the mesonaphric IWofffian) duct, which gives rise to the urataric llud and contributes to the male rapruductiva tract. 3. The matanephros develops from the ureteric bud and forms the adult kidney, which ascends from the sacral region to the upper lumbar region. • The ureteric bud forms the ureter, which dilates at its upper end to form the renal pelvis. The renal pelvis repeatedly divides to form the major calyces, the minor calyces, and collecting tubules. Derivatives of the ureteric bud are the urine-collecting portions of the upper urinary tract. • The metaoephric blastema (intermediate mesodenn} forms the urine-forming components of the adult kidney (glomerulus, renal capsule, loops of Henle, and the proximal and distal convoluted tubules}. 4. The urogenital sinus forms from the hindgut The urorectal septum divides the cloaca into the rectum and anal canal posteriorly and the urogenital sinus anteriorly, which forms the bladder and part of the urethra.

B. Urinary bladder Develops from the upper end of the uroganilll sinus, which is continuous with the allantois. 1. The allantois degenerates and forms a fibrous cord in the adult called the urachus. 2. The trigone of the bladder is formed by incorporation of the lower ends of the masonephric ducts into the posterior wall of the urogenital sinus.

C. Saprarenal gland 1. The cortex forms as a result of two waves ofmasodann proliferation. a. The first wave of the coelomic mesothelial cells forms the fetal cortex. b. The second wave of cells surrounds the fetal cortex and forms the adult cortex. 2. The medulla forms from neural crest calls which invade through the developing cortex and differentiate into chromaffln cells.

144

BRS Graa Allatamy

Ill. POSTERIOR ABDOMINAL BLOOD VESSELS AND LYMPHATICS A. Aoltl (see Figures 4.8 and 4.18) • Passes through the aortic hiatus in the diaphragm at the level of Tl2, descends anterior to the vertebral bodies, and bifurcates into the rigllt and left common iliac arteries anterior to IA. • Gives rise to the following: 1. Inferior phrenic artari11 • Arise from the aorta immediately below the aortic hiatus, supply the diaphragm, and give rise to the superior supraranal arteries. • Diverge across the crura of the diaphragm, with the left artery passing posterior to the esophagus and the right artery passing posterior to the IVC.

2. Middle suprarenal arteries • Arise from the aorta and run laterally on the crura of the diaphragm just superior to the renal arteries.

3. Renal arlllrias •

• •

Arise from the aorta inferior to the origin of the superior mesenteric artery. The right artery is longer and a little lower than the left and passes posterior to the IVC; the left artery passes posterior to the left renal vein. Give rise to the inferior suprarenal and ureteric arteries. DMdein!D thesuperim; anterosuperior, anteroinfurlor, inferim; and posterlar segmenmlbranches.

4. Tasticul1r or avarian arteries •

Descend retroperitoneally and run laterally on the psoas major muscle and across the ureter. (a) The testicular artary accompanies the ductus deferens into the scrotum, where it supplies the spermatic cord, epididymis, and testis.

(bl The DYBrian artery enters the suspensory ligament of the ovary, supplies the ovary, and anastomoses with the ovarian branch of the uterine artery.

5. Lumbar anerin • •

Consist offour or five pairs that arise from the back of the aorta. Run posterior to the sympathetic trunk, the IVC (on the right side), the psoas major muscle,

the lumbar pl.ems, and the quadratus lumborum. Divide into smaller anterior branches (to supply adjacent muscles) and larger posterior branches, which accompany the dorsal primary rami ofthe corresponding spinal nerves and dMde into spinal and muscular branches. 6. Median (middle) sacral artery • Arises from the posterior ofthe aorta proximal to its bifurcation, descends on the anterior of the sacrum, and ends in the coccygeal body. • Supplies the rectum and anal canal and anastomoses with the lwnbar branch of the iliolumbar artery and the lateral sacral artery. •

B. Inferior vana cava • Is formed on the right side of L5 by the union of the two cammon iliac veins, inferior to the bifurcation of the aorta. • Is longer than the abdominal aorta and ascends along the right side of the aorta. • Passes through the opening far the IVC in the central tendon of the diaphragm at the level of TB and enters the right atrium of the heart. • Receives the right gonadal, suprarenal, and inferior phrenic vein&. On the left side, these veins usually drain into the left renal vein. • Receives the right and left renal veins. The left renal vein runs posterior to the superior mesenterlc artery and anterior to the abdominal aorta. • Also receives the three (left, middle, and right) hepatic vain1. The middle and left hepatic veins frequently unite for approximately 1 cm before entering the vena cava.

C. Cistama chyli • Is the lower dilated end of the thoracic duct and lies ju.st to the right and posterior to the aorta, usually between the two crura of the diaphragm. • Is formed by the union ofthe intestinal and lumbar lymph trunks.

l3lJ'1CZJ Abdomen

145

D. Lymph nodes related to the aortl 1. Preaortic nod11 • Include the celiac, superior mesenteric, and inferior mesenteric nodes, which are located around the base of the corresponding arteries. Drain lymph from the GI tract, spleen, pancreas, gallbladdei; and liver. • Their efferent vessels unite to form the intestinal trunk. Z. Para-aortic. lumbar. or lataral aortic lymph nadas • Lie anterior to the lumbar vertebrae beside the aorta and drain lymph from the kidneys, suprarenal glands, testes or ovaries, upper body and fundus of the uterus, and uterine tubes. Receive lymph from the common, internal, and external Iliac lymph vessels. Their efferent vessels unite to form the right and left lwnbar trunks.

IV. NERVES OF THE POSTERIOR ABDOMINAL WALL A. Lumbar plaxus (see Figure 4.19) • Is funned by the union of the ventral rami ofthe first three lumbar nerves and a part of the fourth lwnbar nerve. • Lies anterlorto the transverse processes oftheJumbarvertebraewithJn the substance ofthepsoasmuscle.

Esophagus

Subc:oatalnerve--+++i---""""7l~

~..,_....,,..,+--Subcostal (T12)

Qua:..'\I llgament Greater sciatic foramen--''-'---......_-

RGURE 5..9. Lateral view of the hip bone.

B. Upper pelvic aperture (pelvic inlet or pelvic brim) • Is the saparior rim DI the palvic cavity and is bounded posteriorly by the promontory of the sacrum and the anterior border of the ala of the sacrum !sacral part), laterally by the arcuate or iliopectineal line of the ilium (iliac part) and anteriorly bythe pectineal line, the pubic crest, and the superior margin of the pubic symphysls (pubic part). • Is measured by using transverse, oblique, and anteroposterior (conjugate) diameters. • Is crossed by the urete:i; gonadal vessels, median sacral vessels, iliolumbar vessels, sympathetic trunk, lumbosacral trunk, obturator nerve, spermatic cord, round ligament of the uterus. and suspensory ligament of the avary.

lllac crest

Iliac fossa-..,...,,,....--

Anterior-superior Iliac spine Antertor-lnfertor lllac spine

Ill-"-~~...._ Secrotuberous

E---====:!-- Sacrospinous

Pubic tubercle

lschlal tuberoslty

Obturator foremen RGURE5.1D. Medial view of the hip bone.

ligament

ligament

l3lJ1lm Perineum and Pelvis Body

Malepalvls

113

Iliac Iossa

Female palvla

RGURE 5.11. Mala and lamala pelvic bonas.

C. l.Dwer pelvic aperture (pelvic outlet) • 18 a diamond-shaped epartura bounded posteriorly by the sacrum and coccyx; laterally by the ischial tuberosities and sacrotuberou.s ligaments; and anteriorlyby the pubic sym.physis, arcuate pubic ligament, and rami of the pubis and ischium. • 18 closed by the pelvic and urogenital diaphragms. D. Pelvis major (false pelvis) • Is the expanded portion ofthe bony pelvis above the pelvic brim. It supports abdominal contents and aids in supporting the gravid uterus.

E. Pelvis minor (true pelvis) • Is the cavity ofthe pelvis below the pelvic brim (or superior aperture) and above the pelvic outlet (or inferior aperture), Has an outlet that is closed by the coccygeus and levator ani muscles and the superior perlneal fascia, which form the floor of the pelvis. F. Differtnct1 between the female and male pelvis (Table 5.2) The banes of the female pelvis are usually smaller, lighter, and thinner than those of the male. • The inlet is transversely oval in the female and heart shaped in the male. • The oullllis largarlnthe female thanInthe male becauseofthe evertedischlal tuberositles Inthe female. • The cavity is wider and shallower in the female than in the male. The subpubic angle or pubic arch is larger, and the greater sciatic notch is wider in the female than in the male. • The female sacrum Is shorter and wider than the male sacrum. • The obturatar fora man is oval or triangular in the female and round in the male.

table

52

Differences Between the Female and Mela Pelvis Fa....

Male

Banas Inlet Outlet Cavity

Smaller, lightsr, thinner Transversely oval Larger Wider, shallower

Larger, heavier, thickar Heart-sh1 ped Smaller

Subpubic angla Sacrum ObbJratQr fora man

Larger, greatsr Shorter, wider OvaI or1riangular

Narrawar. duper Sm alier, lesser Longer, narrower Round

184

BRS Graa Allatamy

II. JOINTS OF THE PELVIS (see Figures 5.10 and 5.11) A. Lumbosacral joint • Is the joint between vertebra LS and the base ofthe sacrwn, joined by an intervertebral disk and

supported by the illolumbar ligaments.

B. Sacroiliac joint • Is a synovial joint ofan irregular plane type between the articular surfaces of the sacrum and ilium. • Is covered by cartilage and is supported by the anterior, posterior, andinterosseous sacroiliac ligament.a. • Transmits the weight of the body to the hip bone.

C. Sacrococcygeal joint • Is a cartilaginous joint between the sacrum and coccyx, reinforced by the anterior, posterior, and lateral sacrococcygeal ligaments.

D. Pubic symphysis • Is a cartilaginous or fibrucartilaginous joint between the pubic bones in the median plane.

Ill. PELVIC DIAPHRAGM (see Figure 5.5) • Forms the pelvic floor and supporll all of the pelvic viscera. • Is formed by the llMltor ani and coccygeus muscles and their fascia! coverings. • Ues posterior and deep to the urogenital diaphragm and medial and deep to the ischlorectal fossa. On contraction, rains the entire pelvic floor. Flexes the anorectal canal during defecation and helps the voluntmy control of micturition. • Helps direct the fetal head toward the birth canal at parturition.

IV. LIGAMENTS OR FOLDS AND POUCHES OF THE PELVIS A. Broad ligament of the ut1ru1 (Figures5.12 and 5.13) • Consists oftwo layers of peritonaum, extends from the lateral margin ofthe uterus to the lateral pelvic wall, and serves to hold the uterus in position. • Contains the uterine tube, uterine vessels, round ligament ofthe uterus, ovarian ligament, ureter (lower part), uterovaglnal nerve plexus, and lymphatic vessels. • Does not contain the ovary but gives attachment to the ovary through the mtsovarium.

Mesosalpinx

\

/~esovartum

--i_,f-Mesometrium RGURE 5.12. Sagittal SE1c1ion of the broad ligament

l3:IIJ'rn ovarian ligament

Perineum and Pelvis

185

Fundus of uterus

ovartan

ovary

artery

External os RGURE 5.13. Fam1la reproductive organs. • Haa a posterior layer that curves from the isthmus of the uterus (the ractouterina fold) to the posterior wall of the pelvis alongside the rectum.

1. Muovarium •

Is a fold of peritoneum that connects the anterior surface of the ovary with the posterior layer of the broad. ligament

2. Mesosalpinx • Is a fold of the broad ligament that suspends the uterine tuba.

3. Muomelrium •

Is a major part of the broad ligament below the mesosalpinx and mesovarium.

B. Round ligament of the uterus • Is attached to the uterus in front of and below the attachment of the uterine tube and represents

the remains of the lower part of the gubernaculum. • Runs within the layers of the broad ligament, contains smooth muscle fibers, and holds the fundus of the uterus forward, keeping the uterus anteverted and anteflexed. • Enters the inguinal canal at the deep inguinal ring, emerges from the superficial inguinal ring, and becomes lost in the subcutaneous tissue of the labium majora.

C. Ovarian ligament • I& a fibromuscular cord that extends from the ovary to the uterus belowthe uterine tube, running within the layers of the broad ligament. • Represents the remains of the upper part of the gubemaculum.

D. Suspensory ligament of the ovary • Is a band of peritonaum that mends upward from the ovary over the posterior pelvic brim and transmits the ovarian vessels, nerves, and lymphatics.

E. Lataral or transvarsa cervical (cardinal or Mackanrodt) ligaments of Iha uterus • Are fibromuscular cond1nsation1 of pelvic fascia from the cervix and the vagina to the pelvic walls, extend laterally below the base of the broad ligament, and support the uterus.

F. Pubocervical ligaments • Are finn bands of connective tissue that extend from the posterior surface of the pubis to the cervix of the uterus.

1•

BRS Grass Anatomy

G. Pubovesical !female) ar puboprostatic (male) ligaments • Are condensations of the pelvic fascia that extend from the neck of the bladder (or the prostate gland in the male) to the pelvic bone. H. Sacracervical ligaments Are firm fibromuscular bands of pelvic fascia that extend from the lower end of the sacrum to the cervix and the upper end of the vagina. I. Inferior pubic larcuata pubic) ligament Arch.es across the inferior aspect of the pubic symphysis and attaches to the medial borders of the inferior pubic rami.

J. Ractouterina (11crouterin1) lig1m1nts Hald Ille cervix back and upward and sometimes elevate a shelf-like fold ofperitoneum lrectauterina fold), which passes from the isthmus of the uterus to the posterior wall ofthe pelvis lateral to the rectum. It corresponds to the sacroganital lrtctoprostaticl fold in the male.

K. Ractoutarina pouch ICul-da-sac of Douglas) Is a sac or recess formed by a fold of the peritoneum dipping down betwtlen the rectum and the

uterus. Lies behind the posterior fomix of the vagina and contains peritoneal fluid and some of the small intestine.

L Ractonsical pouch Is a peritoneal recess between the bladder and the rectum in males, and the vesicoutarina pouch is a peritoneal sac between the bladder and the uterus in females.

CLINICAL CORRElATES

Culdocantesis is aspiration of fluid from the cul-de-sac of Douglas (rectouterine pouch) by a needle puncture of the posterior vaginal fornix near the midline

between the uterosacral ligaments. As the lowest portion of the peritoneal cavity, the rectauterina

pouch can collect fluid. This procedure is done when pain occurs in the lower abdomen and peMc regions and a ruptUred ectopic pregnancy or ovarian cyst is suspected.

V. URETER AND URINARY BLADDER (Figures 5.14to 5.16) A. Ureter Is a muscular tuba that transmits urine by peristaltic waves. Has1hrt1 constrictions along its course: at its origin where the renal pelvis joins the ureteIJ where it crosses the pelvic brim, and at its junction with the bladder. Crosses the pelvic brim in front of the bifurcation of the couunon iliac artery; descends retroperltoneally on the lateral peMc wall; and runs medial to the umbilical artery and the obturator vessels and posterior to the ovary, forming the posterior boundary of the ovarian fossa. In females, it is distally accompanied in its course by the uterine artery, which runs above and anterior to it in the base of the broad ligament of the uterus. In males, it passes posterior and inferior to the ductus deferens and J.iea in front of the seminal vesicle before entering the posterolateral aspect of the bladdeL • Enters obliquely through the base of the bladder and opens by a slit-like orifice that acts as a valve, and the circular fibers of the intramural part of the ureter act as a sphincter. When the bladder is distended, the valve and sphincter actions prevent the reftwc ofurine from the urinary bladder into the ureter. Receives blood from the aorta and the renal, gonadal, common and internal iliac, umbilical, superior and inferior vesical, and middle rectal arteries.

i3JIJ'ltlij Perineum and Pelvis

187

Urinary bladder---+---

Ampullaof

ductus defarens--'1-..._......,_-=·--.

A

Semlnal colllculua

c

Ejaculatory ductB

RGURE 5.14. Male urogenital organs. A:. A posterior view of the bladder and male accessory organs. B: A midsaggital view of the prostate gland showing prostatic zones. C: A crou section of the prostate showing lobes and internal prostatic ltructures.

CUNICAL CORRELATES

Damage to the ureter: In the female, damage may occur during a hysterectomy

or surgical repair of a prolapsed uterus because it runs under the uterine artery. The ureter is inadvertently clamped, ligated, or divided during a hysterectomy when the uterine artery is being ligated to control uterine bleeding. This relationship can be remembered by the mnemonic device, ·water (ureter) runs under the bridge (uterine artery)...

188

IRS Gross Anatomy Rectus abdomlnls Ileum

Common Iliac artery Descending ccIon Ureter Psoasmajor Gluteus medius

Femoral artery

Bladder

Femoral vein ~;;t;i~!-. Obturaklr V9889l8

Seminal vesicle

Spermatic cord Femoral artery

Sartorius Rectus femorts _ Tensor -!!~ti fasciae latae

Femoral vein

Prostallcurethra

Gluteus maximus Spermatic cord

Pectineus Femoral artery

Pectlneus

Deep femoral artery Femoral vein Adductor magnus Quadratus femorls ladilorectal

- -..u

..,....,._ii'-_

Adductor longus musde lschiocavemosus {Crus of penis) Bulbosoongloeus (Bulb o'f penis) Pudenda! canal Anal canal

fossa

FIGURE 5.15. Computed tomography scans of tile male pelvis and perineum.

B. Urinary bladder Is situated below the peritonewn and ls slightly lower in the female than in the male. Bx:tends superiorly above 1he pelvic brim into the abdominal cavity as it fills. The apex projects anterosuperiorly towards the pubic symphysis and 1he fundus or b111 forms its posteroirller:ior triangular portion. Has a neck, which is the area where the fundus and the irUerolateral surfaces come togethei; leading into the uredlra.

l31trall:J

Neck of lam.tr

Perineum and Pelvis

189

~S~~5;!!,- Femora1w1n '-';fi:.Ill~,~~~~;-- Uterine cervix

ereater trochantllr Obturator lnternus muscle Gluteus maximue

~rfor gemellus

Rectum

Labium majus

Obturator extemus

Quadratus femorll llld!lal tuberoelty~::::::;;::;::::::::~ 0iute1J1 ma>dmus

muscle

Anal canal

FIGURE 5.16. Computed tomography scans of tile female pelvis and perineum.

Has a uvula, which is a small eminence at the apex ofits trigone, projecting into the orifice ofthe urethra. The trigone is bounded by the two orifices of the ureters and the internal urethral orifice, around which is a thick circular smooth muscle layer called the internal sphincter (sphincter

vealcae). Has bWldles of smooth muscle ftbera ln lts walls known as the datrusor muscle af1fte bladder. Receives blood from the superior and Inferior vesical arteries (and from the vaginal artery in females). Its venous blood is drainedby the prostatic (ar vesical) plexus of veins, which empties into the Internal iliac vein. Is innervated by nerve fibers from the veslcal and prostatic plexuses. The par1sympatftstic nerves (pelvic splanchnic nerves originatingfrom S2-S4) stimulate contraction of the musculature (de-

trusor) ofthe bladder wall, minorly contribute to the relaxation ofthe internal urethral sphinctei; and promote emptying. The qmpatftttic nerv11 constrictthe intemal urethral sphincter and the trigone region of the bladder. Sympathetic fibers also innervate the vasculature of the bladder.

CUNICAL CORRELATES

Bladder cancer usually originates in cells lining the inside of the bladder (epithelial cells). The most common symptom is blood in the urine (hematuria). Other symptoms include frequent urination (polyuria) and pain upon urination (dysuria). This cancer may be induced by organic carcinogens that are deposited in the urine attar being absorbed from the environment and also by cigarette smoking. T1n11mus is a constant feeling of the desire to empty the bladder or bowel, accompanied by pain, cram ping, and straining due to a spasm of the urogenital diaphragm. lntlmitial cystitis is a chronic inflammatory condition of the bladder that causes frequent, urgent, and painful urination. This can occur with frequent urinary tract infections and chemical exposure.

C. Urethra It serves as a passage for urine from the urinary bladder to the exterioz; but in men, it also serves as a passage for semen. Male urethra is approximately 20 cm long and consists of three parts: prostatic, membranous, and spongy. The lowest part of the membranous urethra is susceptible to rupture or to penetration by a catheter.

BRS Graa Allatamy

190

• Female urethra ls approximately 4 cm long, and its external urethral orifice is situated between the labia minora, anterior to the vaginal opening, and posterior to the glans clitoris. • The male urethra is supplied by the urethral artery whereas the female urethra is supplied by the vaginal and inferior vesical arteries.

D. Micturition (urination) • Is initiated by stimulating stretch receptors in the detrusor muscle in the bladder wall as the urine volume increases (approximately 400 mL for adults). • Can be assisted by contraction of the abdominal muscles, which increases the intra-abdominal and pelvic pressures. • Involves the following processes: 1. Sympathetic (visceral efferent [VE]) fibers constrict the internal sphincter, inhibiting emptying. (They also activate during ejaculation to constrict the internal sphincter in order to prevent seminal reflwc into the bladder.) 2. Visceral afferent IVA) impulses arise from stretch receptors in the bladder wall and enter the spinal cord (S2-S4) via the pelvic splan.chnic nerws. 3. Parasympathetic pregangllonic (VE) fibers in the pelvic splanchnic nerves pass through the pelvic (inferior hypogastric) plexus to synapse within the bladder wall; postganglionic fibers to the bladder musculature induce a refteJ: contraction ofthe detrusor muscle and :relaxation of the internal urethral sphincter in concert with reduced stimulation by sympathetic fibers. 4. Somatic efferent fibers in the pudenda! nerve cause voluntary relaxation of the extemal urethral sphinctei; and the bladder begins to void. 5. At the end of micturition, the external urethral sphincter contracts, and bulbospongiosus muscles in the male expel the last few drops of urine from the urethra.

VI. MALE GENITAL ORGANS (Figures 5.17 and 5.18; see also Figures 5.14 and 5.15) A. Tellis • Develops retroperitoneally and descends into the scrotum retroperitoneally. • Is covered bythetunil:a albuginea, which lies beneath the visceral layer of the tunica vaginalis. • Praduces spennatazoe within the seminiferous tubules and interstitial cells (of LeydJg) secrete tastosterane.

Ureter

Glans penis

RGURE 5.17. Mala raproductive organs.

l3lJ1lm Perineum and Pelvis Sigmoid colon\

u....,~-

Ureter\

D

191

Cj

c;...· '\\\ ~~

Peritoneum - -

Rectum Rectoveslcal

pouch

'-,,.,..=.,~.!;--ttr--Ampulla o1 ""' ductus daferens +--'-- ---'--1-r-----Semlnal vesicle

Symphysis pubis---

Ejaculatory duct Pl'OIJlate gland ..::..:::7"-::z:- - - - - - - - - U r o g e n l t a l diaphragm - External anal ~:r------r-r----

Corpus cawrnosum penis-- / Corpus sponglosum penls---:-

1

Testicular artery and vein--'--+- _,,., Head of epididymis--+---i""=-

-

sphincter muscle

Glans penis

Testis

Anal canal

Bulbourethral gland and duct Bulb of penis RGURE 5.1L Sagittal section of 1f1a male pelvis.

Is supplied by the testicular artery from the abdominal aorta and is drained by veins ofthe pampiniform plems into the testicular veins, of which the left drains into the left renal vein and the right drains directly into the inferior vena cava.. • Hu lymph vessels that ascend with the testicular vessels and drain into the lumbar (aortic) nodes; lymphatic vessels in the scrotum drain into the superficial inguinal nodes.

CLINICAL

Testicular torsion is the twisting of a testis and the spermatic cord, obstructing blood supply to tile testis, and causing sudden urgent pain and swelling of the scrotum or nausea and vomiting. It is most common during adolescence and may be caused by trauma or a spasm of tile cremaster muscle. Testicular torsion requires emergency treatment and if not untwisted, testicular necrosis will occur. Orchitis is the inflammation of'llle testis and is marted by pain, swelling, and a feeling of heaviness in the testis. It may be caused by mumps, gonorrhea, syphilis, or tuberculosis. If testicular infection spreads to the epididymis, it is called apididymo-orchitia. Tlllticular cancer develops commonly from the rapidly dividing early-stage spermatogenic cells (seminoma or germ cell tumor). Tumors can also develop from Laydig cells, which produce androgen (Laydig call tumor), and Sertoli calls, which support and nourish germ calls and produce androgen-binding protein and 'Ille hormone inhibin (Sertoli-cell tumor). Si9ns and symptoms include a painless firm mass or lump, testicular swelling, hardness, and a feeling of heaviness or aching in the scratum or lower abdomen. The cause of cancer is unknown, but same major risk factors include cryptorchidism and Klinefelter syndrome (47, XXY sax chromosome, seminiferous tubule dysganesis, gynecomastia, and infertility). Metastasis occurs via lymph and blood vessels. It can be treated by the surgical removal of the affected testis and spennatic cord (orchiectomy), radio'lllerapy, and/or chemotherapy. CryptDn:hidism is a congenital condition in which the testis fails to descend into tha scrotum during fetal development Undescended tastes are associated with reduced fertility, increased risk of testicular cancer, and higher susceptibility to testicular torsion and inguinal hernias. Undescended tastes are brought down into the scrotum in infancy by a surgical procedure called an orchiopexy or orchidopexy.

CORRELATES

192

BRS Gross Anatomy

B. Epididymis

convoluted duct approximately 6 m (20 ft) long that connects the efferent ductules of the testis to the ductus deferens. Consists of a head, body, and tail. • Functions in the maturation 1nd 11orage of spermatozoa. • Is a

C. Ductus dtf1ren1 • Is continuous with the tail of the epididymis and serves to transport sperm to the ejaculatory

duct(s} prior to ejaculation. Is a thick-walled tube that ascends within the spermatic cord to enter the peMs at the deep inguinal ring lateral to the inferior epigastric artery. • Courses medial to the umbillcal artery and obturator nerve and vessels, passes superior to the ureter near the wall of the bladder, and is dilated to become the ampulla at Its terminal part at the base of the prostate. • Innervation is primarily from postganglionic sympathetic nerves of the pelvic plexus that cause peristaltic contractions that propel spermatozoa into the ejaculatory duct.

CLINICAL CORRELATES

Vanctomy is tfle surgical excision of a portion of the vas deferens (due1Us

deferens) through the scrotum. It stops the passage of spermatozoa but neither reduces the amount of ejaculate greatly nor diminishes sexual desire.

D. Ejaculatory ducts Are formed by the union of the ductus deferens with the ducts of the seminal vesicles. Peristaltic contractions of the muscular layer of the ductus deferens and the ejaculatory ducts propel spermatozoa with seminal fiuid into the urethra. Open into the prostaticurethra on the uminal colliculus justlateral to the blind prostatic utricle.

E. Seminal YG1icln Are enclosed by dense endopelvic fascia and are lobulatad glandular structures that are diver-

ticula of the ductus deferens. • Ue inferior and lateral to the ampullae of the ductus deferens against the fund.us (base} of the

bladder. Produce an alkaline secretion containing fructasa and choline, which will be mixed with the contents ofthe duc:tus daferans and secretions ofthe prostate and bulbourethral glands to make up the nminal fluid. Have lower ends that become narrow and fonn ducts, which join the ampullae of the ductus deferens to form the ejaculatory ducts. Do not store spermatozoa, as was once thought; this is done by the epididymis, the ductus deferens, and its ampulla.

CLINICAL CORRELATES

Seminal vesicles produce the alkaline constituent of the seminal fluid, which contains fructose end choline. Fructose provides e forensic determination for occurrence of rape, where es choline crystals provide tfle basis for tfle determination of the presence of semen (Florance test).

F. Prostate gland • Is located at the base of the urinary bladder and consists chiefly of glandular tissue mixed with

smooth muscle and fibrous tissue. Has four zones: the anterior zone (or isthmus), which lies in front of the urethra and is devoid of glandular substance; the b'ansitional zana, which encompasses the urethra prmdmal to the ejaculatory ducts and ls prone to banign hypertrophy obstructing the internal urethral orifice; the central zone, which encompasses the ejaculatory ducts up to the urethra; and the peripheral

l3lJ1lm Perineum and Pelvis

193

zone, which is situated posteroinferlor and lateral to the transitional and central zones, forming the main mass of the gland and is thus the most prone to carcinomatous transf'Ormation. • Secretes a ftuid that produces the characteristic odor of semen. This ftuid, the secretion from the seminal vesicles and the bulbourethral glands, and the spermatozoa constitute the umen or seminal fluid. Secretes prostata-1pacific antigen (PSA), prostaglandins, citric acid and acid phosphatase, and proteolytic enzymes. • Has ducts that open into the prostatic sinus, a groove on either side of the urethral crnt. Receives the ejaculatory duct. which opellll into the urethra on theseminal colliculu1 just lateral to the blind prDllatic utricle. • The proatate gland was previouslydescribed as consisting offive ill-defined lobes (see Figure 5.14C). The zonal description is based on histologic features unique to each zone.

CLINICAL CORRELATES

Hypertrophy al the prostate is a benign enlargement of the prostate that affects older men and occurs most often in the lnlnsitianal zane, obstructing the internal urethral orifice and thus leading to nocluria (excessive urination at night), dysuria (difficulty or pain in urination), and urgency (sudden desire to urinate). Prostatitis is the inflammation of the prostate. Prastate cancer is a slow-growing cancer that occurs particularly in the peripheral zone. It is usually symptomless in the early stages, but it can impinge on the urethra in the late stage. Prostate cancer spreads to the bony pelvis, pelvic lymph nodes, vertebral column, and skull via the vertebral venous plexus, producing pain in the pelvis, the lower back, and the bones. This cancer also metastasizes to the heart and lungs through the prostatic venous plexus, internal iliac veins, and into the inferior vena cava. It can be detected by digital rectal examination, ultrasound imaging with a device inserted into the rectum, or PSA test PSA concentration in the blood of normal males is less than 4.0 ng/ml. Prostatectomy is the surgical nmoval of a part or all of the prostate gland. Perinea! prostatectomy is removal of the prostate through an incision in the perineum. Radical prostatectomy is removal of the prostate with seminal vesicles, ductus deferens, some pelvic fasciae, and pelvic lymph nodes through the retro pubic or the perinea! route. Transurethral resection of the prostate llURP) is the surgical removal of the prostata using a cystoscope passed through the urethra. Acareful dissection of the pelvic and prostatic nerve plexuses is required during prostatectomy to avoid loss of erection and ejaculation.

G. Urethral crest Is located on the posterior wall of the prostatic urethra, which has numerous openings for the prostatic ducts an either side. • Has an ovoid-shaped enlargement called the seminal coIiicul us (Y8rumontanum), upon which the two ejaculatory ducts open. At the summit of the colllculus ls the prostatic utricle, which is an invaglnatlon (a blind pouch) approximately 5 mm deep; it is analogous to the uterus and vagina in the female. H. Prostatic sinus Is a groove between the urethral crest and the wall ofthe prostatlc urethra and receives the ducts of the prostate gland. I. Erection Depends on stimulation of parasympalhetics from the pelvic splanchnic nerves, which dilates

the arteries supplying the erectile tissue and thus causes engorgement of the corpora cavernosa and corpus spongiosum. compressing the veins and thus impeding venous return and causing full erection. • Is also maintained by contraction of the bulbospongiosu1 and i1chiacanrna1u1 muscles, which compresses the erectile tissues of the bulb and the crus. Is often described using a popular mnemonic: point (erection by parasympathetic) and shoot (ejaculation by sympathetic).

194

IRS Gross Anatomy

J. Ejaculation Begins with nervous stimulation. Friction to the glans penis and other sexual stimuli result in excitation af sympathetic fibers, lead.Ing to contraction of the smooth muscle of the epldidymal ducts, the ductus deferens, the seminal vesicles, and 1he prostate in turn. Occurs as a result of contraction of the smooth muscle, th.us pushing spermatozoa and the secretions of both the seminal vesl.cles and prostate into the prostatic urethra, where 1hey Join secretions from the bulbouretlual and penile urethral glands. All of these secretions are ejected together from the penile urethra because of the rhydunic contractions of the bulbospongiosus, which compresses the urethra. Involves sympathetic contraction of the sphincter of the bladder, preventing the entry of urine Into the prostatic urethra and the renu:x: of the semen into the bladder.

VII. FEMALE GENITAL ORGANS (Figure 5.19; see also Figures 5.13 and 5.16) A. Ovaries Lie on the posterior aspect of the broad ligament on the side wall of the pelvis minor and are bounded by the external and internal iliac veasels. Ase not covered by the peritoneum, and thus, the ovum or oocyte Is expelled Into the peritoneal cavity and then into the uterine tube. Ase not enclosed in the broad ligament, but their anterior Slll'face is attached to the posterior layer of the broad ligament by the mnovarium. Have a surface that is covered by germinal (columnar) epidaelium, which is modified from the developmental peritoneal covering of the ovary. Ase supplied primarily by the ovarian arteries, which are contained in the suspensory ligament and anastomosewith branches ofthe uterine artery. Ase drained by 1he ovarian veins; the right ovarian vein joins the inferior vena cava, and the left ovarian vein joins the left renal vein.

CUNICAL CORRELATES

Ovarian cancer develops from germ cells that produce ova or eggs, stromal cells that produce estrogen and progesterone, and epithelial cells 1hat cover the outer surface of the ovary. Unfortunately, symptoms develop much later in the stage of disease and include a feeling of pressure in the pelvis or changes in bowel or bladder habits. Diagnosis involves palpating a mass during a pelvic examination, visualizing by vaginal ultrasound, or using a blood test for a protein associated with ovarian cancer (CA-125). Some germ call cancers release certain protein markers, such as human chorionic gonadotropin and cx-fetoprotein, into the blood. Cancer signs and symptoms include unusual vaginal bleeding, postmenopausal bleeding, bleeding after intercourse, pain during intercourse, pelvic pressure, abdominal and pelvic pain, back pain, indigestion, and loss of appetite.

B. Uterine tubea EKtend from the uterus to the uterine end of the ovaries and connect the uterine cavity to the peritoneal cavity. Ase each subdivided into four parts: the uterine part, the isthmus, the ampulla (the longest and widest part), and the infundibulum (the funnel-shaped termination formed offimbri11). Convaytht fertilized or unfertilized oocytes to the uterus by clliaryaction and muscular contraction. Transport spermatozoa In the opposite direction (toward the eggs); fertilization takes place within the tube, usually in the infundibulum or ampulla. Fertilization ls Initiated by penetration of the secondary oocyte by the sperm and completed by fusion of the male and female pronuclei.

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Flmbrta.-T'-'T:;-;."" Anterior nasal spine -Cl~~~-~lr-Coronold process ""+H-r-1~~--'-.,..--!_..~i!t-Neck

Zygomatic arch

Mandible Temporal proceaa of zygomatic bone

RGURE I .ti. Latl!ral view of111e skull.

Condylokl

{ Head~

Mandibular notch

I

~u -~=~~

.

~Alveolar process

Mental tubercle

Pterygold Iossa Coronoid process

Mental spine (gtnlal tubercle)

RGIURE B.11. External (buccal) and internal (lingual) surfaces of the mandible.

Head } Condylold Neck process

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371

3. Superior •

Temporal line.

4. Lateral •

Zygomatic arch.

5. Inferior •

Infratemporal crest.

&. Floor • Parts of the frontal, parietal, temporal, and greater wing of the sphenoid bone.

B. lnfratemporal Iossa (see Figures 8.18 and 8.19) • Contains the inferior portion ofthe temporalis muscle, the lateral and medial pterygoid muscles, the pterygoid plexus oheins, the mandibular nerve and its branches, the maxillary artery and its branches, the chorda tympani, and the otic ganglion. • Hu the following boundaries:

1. Anterior • 2.

Posterior surface of the maxilla.

Postarior •

Styloid and mastoid procesaes.

3. Medial •

Lateral pterygoid plate of the sphenoid bone.

4. Lateral •

Ramus and coronoid process of the mandible.

5. Roof •

Greater wing of the sphenoid and infratemporal crest.

II. MUSCLES OF MASTICATION (see Figure 8.20; Table 8.4) Mandibular nerve Mlddle meningeal artery

Deep temporal nerves and artery

·llH-'lt-+--+---+--+-Temporalls muscle Lateral pterygold muscle ~ll!F+--+-...i.,, ,...Sphenopalatine artery

Chorda tymparf , Postertor auricular artery ~"\S

Facial nerve~

Maxillary artery---1~--=

_

n~s;,,....,...

___,,,_Descendlng palatine ""-artery ~--......,_-lnfraorbital artery

~-:------___.,..

Occipital artery Inferior elveolar--~o:artery and nerve Medial pterygold muscle-.....-::::;~~r""t: Lingual nerve Masseter muscle Internal carotid artery External carotid artery Common carotid artery Superior thyroid artery Inferior allleolar nerw

RGURE llD. lnfratemporal region.

Posterior-superior

alveolar artery

Mandlble

BRS Gross Anatomy

3n t

8.4

a b I e

Muscles of Mastication

Musci.

OritiIn

l1111rtlan

N1rve

Al:llDI an M1ndlbll

Tamporalis

Temporal fosaa

Trigaminal

Elavatas; ratracts

Massmr

Lower border ind medial surface of Z\'llOmatic arch

C:oronoid procass and ra mus of mandib11 Llltllnil surface of coronoid process, ra mus 1 nd angle of mandibla

Trigeminal

Elevates (superficial part); retracts (deep part)

Lateral ptarygoid

Superior haad from infratempora1surfaca of sphanoid; inferior head from lataral surfac1 of lataral pta rygoid plalll of 1 phanoid Tuber of maxilla (superficial headt medial surface of lateral ptarygoi d plats; pyramidal procns of palatine bone (daap head)

Neck of mandible; articular disk and ca psula of tsmporomandibular joint

Trigeminal

Depressu (1u parior haad); protracts linfarior haad)

Medial surface of angle and ram us of mandibla

Trigeminal

Elevates; protracts

Medial pterygoid

The jaws ;re opened 17{1he lateraI pterygoid muscle and are closed b'f 1he telrfloralis. masseter. and medial pteiygoid muscles.

Ill. NERVES OF THE INFRATEMPORAL REGION (see Figure 8.20) A. Mandibular division of Ille trigeminal nerve • Exits the skull through the foraman nala and innervates the tensorveli palatini and tensor tympani muscles, muscles of mastication (temporalls. masseter, and lateral and medial pterygoid), anterior belly of the digaatric muscle, and the mylohyoid muscle. • Provides sensory innervation to the lower teeth and gums and to the facial skin below the mouth and lower lip. • Gives rise to the following branches:

1. Meningeal branch •

Accompanies the middle meningeal artery, enters the cranium through the foramen

spinosum, and supplies the meninges of the middle cranial fossa. 2. Muscular branches •

Include masseteric, deep temporal, medial, and lateral pterygoid nerves.

3. Buccal narve • •

Descends between the two heads of the lateral pterygoid muscle. Innervates skin and fascia on the bu.cclnator muscle and penetrates this muscle to supply the mucous membrane of the cheek and gums.

4. Auriculotemporal nelY8 •

Arises from two roots that encln:le the middle meningeal artery.

•

Carries pDllganglionic parasympathetic and sympathetic VB fibers to the parotid gland and SA sensory fibers from the temporomandibular joint and the skin of the auricle and the scalp.

CLINICAL CORRELATES

Frey syndrome produces flushing and sweating instead o1 salivation in response to taste of food after injury of tha auriculatamporal nerve, which carries parasym patlletic secretomotor fibers to 1tle parotid gland and sympathetic fibers to tile sweat glands. When tile nerve is severed, the fibers can regenerate along each other's pathways and innervate tile wrong gland. It can occur after parotid surgery and may be tr1&tad by cutting tile tympanic plexus in the middle ear.

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5. Lingual RIMI Descends deep to the lateral pterygoid muscle and provides gener1l 11n11tion from the anterior two-thirds of the tongue. !tis joined by the chord• tympani, which conveys preganglionic p1n1sympatll1tic (VE) fibers to the submandibular ganglion and taste fibers from the anterior two-thirds of the tongue. Lies on the medial pterygoid muscle, deep to the ram.us of the mandible. Crosses lateral to the styloglossus and hyoglossus muscles, passes deep to the mylohyold muscle, and descends lateral to and loops under the submandlbular duct. 6. Inferior alveolar nerve Passes deep to the lateral pterygoid muscle and then between the sphenomandibular ligament and the ramus of the mandible. Enters the mandibular canal through the mandibular furamen and supplies the tissues of the chin, lower teeth, and gums. Gives rise to the following branches: (a) Mylohyoid nem innervates the mylohyoid and the anterior bellyof the digastric muscle. (b) Inferior dental llrancll innervates lower teeth. (c) Mental nerve innervates the skin over the chin. (d) Incisive branch innervates 1he canine and incisor teeth.

B. Olic ganglion Iles in the lnfratemporal Cossa, justbelow the foramen ovale between the mandibular nerve and the tensorveli palatlni. Receives preganglionic parasympathetic (VE) fibers that run In the glossopharyngeal nerve, tympanic nerve and plexus, and lesser pettosal nerve and synapse in 1his ganglion. Contains cell bodies of postganglionic parasympathetic (VE) fibers that run in the auriculotemporal nerve to innervate the parotid gland.

IV. BLOOD VESSELS OF THE INFRATEMPORAL REGION (see Figure 8.20) A. Maxillary artery Arises from the external carotid artery at the posterior border of the ramus of the mandible. Divides into three parts: 1. Mandibular part Runs anteriorly between the neck of the mandible and the sphenomandlbular ligament and gives rise to the following branches: (a) Deep auricular artery

Supplies the eictemal acoustic meatus. (b)

Anteriortympanic artery Supplies the tympanic ca:vity and tympanic membrane.

(c) Middle mening11l artery Is encircled by two roots of the auriculotemporal nerve, enters the middle cranial Cossa through the f'oramen 1pinosum, and runs between the dura. mater and the periosteum.

CUNICAL CORRELATES

Rupture of the middle m1nin91al 1rtery may be caused by fracture of the sq uamous part of the temporal bone as it runs through the foramen spinosum and just deep to the inner surface of the tempora I bone. It can cause epidural hemato• with increased intracranial pressure.

374

BRS Gross Anatomy

(d) Accessory meningeal artery Passes through the foramen ovale. (e) Inferior alveolar artery Follows the inferior alveolar nerve, gives off the mylohyoid branch, enters the mandibular canal through the mandibular foramen to supply the mandibular teeth, and exits the mandible as the mental artery that supplies the tissues of the chin. Z. Plerygoid part Runs anteriorly deep to the temporalis and superficial or deep to the lateral pterygoid muscle. Branches are the anterior and posterior deep temporal, pterygoid, masseteric, and buccal arteries, which supply chiefly the muscles of mastication. 3. Plerygopalatine part Runs between the two heads of the lateral pterygoid muscle, then through the pterygomaxillary fissure into the pterygopalatine fossa, and has the following branches: (a) Posterior-superior alveolar arteries Run downward on the posterior surface of the maxilla and supply the molar and premolar teeth and the maxillary sinus. (b) lnfraorbital artery Enters the orbit through the inferior orbital fissure, traverses the infraorbital groove and canal, and emerges on the face through the infraorbital foramen. Divides into branches to supply the lower eyelid, lacrimal sac, upper lip, and cheek. Gives rise to anterior and middle superior alveolar branches to supply the upper canine and incisor teeth and the maxillary sinus. (c) Descending palatine artery Descends in the palatine canal and supplies the soft and hard palates. Gives rise to the greater and lesser palatine arteries, which pass through the greater and lesser palatine foramina, respectively. The lesser palatine artery supplies the soft palate. The greater palatine artery supplies the hard palate and sends a branch to anastomose with the terminal (nasopalatine) branch of the sphenopalatine artery in the incisive canal or on the nasal septum. (d) Artery of the pterygoid canal Passes through the pterygoid canal and supplies the superior part of the pharynx, auditory tube, and tympanic cavity. (e) Pharyngeal artery Supplies the roof of the nose and pharynx, sphenoid sinus, and auditory tube. (t) Sphenopalatine artery Enters the nasal cavity through the sphenopalatine foramen in companywith the nasopalatine branch of the maxillary nerve. Is the principal artery to the nasal cavity, supplying the conchae, meatus, and paranasal sinuses and may cause epistaxis (nosebleed) when damaged. B. Plerygoid venous plexus (Figure 8.21) Lies on the lateral surface of the medial pterygoid muscle, receives veins corresponding to the branches of the maxillary artery, and drains into the maxillary vein. Communicates with the cavernous sinus by emissary veins that pass through the fora.men ovale, the inferior ophthalmic vain which runs through the infraorbital fissure, and the facia I vein via the deep facial vein. C. Retromandibular vein Is fanned by the superficial temporal vein and the maxillary vein. It divides into an anterior branch, which joins the facial vein to form the common facial vein, and a posterior branch, which joins the posterior auricular vein to form the external jugular vein.

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Superior petrosal sinus Supertor seglttal sinus

Straight sinus

~~~i!:S,~1Superior ophthalmic vein

Faix cerebelll Transverae sinus

•~___,,.~Inferior ophthalmic vein

..........i---!--!.--Superficial temporal vein

Inferior petrosal sinus ~,,>+.o-+-­ Slgmold slnus---''l;-Maxillary vein

Pterygold plexus ~----'=